diff --git a/Cargo.lock b/Cargo.lock
index 749ca1477..3dd52008b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "aho-corasick"
+version = "1.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c982642fa9e8606056828ee9a8505737230110bb1099153c79efe865c59d12ba"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "allocator-api2"
 version = "0.2.21"
@@ -17,6 +26,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "anes"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b46cbb362ab8752921c97e041f5e366ee6297bd428a31275b9fcf1e380f7299"
+
 [[package]]
 name = "annotate-snippets"
 version = "0.12.16"
@@ -178,6 +193,12 @@ dependencies = [
  "displaydoc",
 ]
 
+[[package]]
+name = "cast"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37b2a672a2cb129a2e41c10b1224bb368f9f37a2b16b612598138befd7b37eb5"
+
 [[package]]
 name = "cc"
 version = "1.2.24"
@@ -193,6 +214,33 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "ciborium"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42e69ffd6f0917f5c029256a24d0161db17cea3997d185db0d35926308770f0e"
+dependencies = [
+ "ciborium-io",
+ "ciborium-ll",
+ "serde",
+]
+
+[[package]]
+name = "ciborium-io"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05afea1e0a06c9be33d539b876f1ce3692f4afea2cb41f740e7743225ed1c757"
+
+[[package]]
+name = "ciborium-ll"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57663b653d948a338bfb3eeba9bb2fd5fcfaecb9e199e87e1eda4d9e8b240fd9"
+dependencies = [
+ "ciborium-io",
+ "half",
+]
+
 [[package]]
 name = "clap"
 version = "4.5.60"
@@ -273,6 +321,46 @@ dependencies = [
  "libm",
 ]
 
+[[package]]
+name = "criterion"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2b12d017a929603d80db1831cd3a24082f8137ce19c69e6447f54f5fc8d692f"
+dependencies = [
+ "anes",
+ "cast",
+ "ciborium",
+ "clap",
+ "criterion-plot",
+ "is-terminal",
+ "itertools 0.10.5",
+ "num-traits",
+ "once_cell",
+ "oorandom",
+ "regex",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "tinytemplate",
+ "walkdir",
+]
+
+[[package]]
+name = "criterion-plot"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6b50826342786a51a89e2da3a28f1c32b06e387201bc2d19791f622c673706b1"
+dependencies = [
+ "cast",
+ "itertools 0.10.5",
+]
+
+[[package]]
+name = "crunchy"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "460fbee9c2c2f33933d720630a6a0bac33ba7053db5344fac858d4b8952d77d5"
+
 [[package]]
 name = "databake"
 version = "0.2.1"
@@ -337,7 +425,7 @@ dependencies = [
  "diplomat_core",
  "heck",
  "indenter",
- "itertools",
+ "itertools 0.14.0",
  "quote",
  "serde",
  "syn 3.0.3",
@@ -390,6 +478,17 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
 
+[[package]]
+name = "half"
+version = "2.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6ea2d84b969582b4b1864a92dc5d27cd2b77b622a8d79306834f1be5ba20d84b"
+dependencies = [
+ "cfg-if",
+ "crunchy",
+ "zerocopy",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.16.0"
@@ -413,6 +512,12 @@ version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
+[[package]]
+name = "hermit-abi"
+version = "0.5.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e17592d60ebacc7d5e169f4663c5f84f9161cc90328abcfe8456f41e4dfcb284"
+
 [[package]]
 name = "iana-time-zone"
 version = "0.1.65"
@@ -565,12 +670,32 @@ dependencies = [
  "hashbrown 0.17.1",
 ]
 
+[[package]]
+name = "is-terminal"
+version = "0.4.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3640c1c38b8e4e43584d8df18be5fc6b0aa314ce6ebf51b53313d4306cca8e46"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "windows-sys",
+]
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7943c866cc5cd64cbc25b2e01621d07fa8eb2a1a23160ee81ce38704e97b8ecf"
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itertools"
 version = "0.14.0"
@@ -662,6 +787,12 @@ version = "1.70.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a4895175b425cb1f87721b59f0f286c2092bd4af812243672510e1ac53e2e0ad"
 
+[[package]]
+name = "oorandom"
+version = "11.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6790f58c7ff633d8771f42965289203411a5e5c68388703c06e14f24770b41e"
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.1"
@@ -706,6 +837,35 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "regex"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f020237b6c8eed93db2e2cb53c00c60a8e1bc73da7d073199a1180401450218d"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-automata",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.4.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad8553b9b26413251cbf30e620595c7a41b3887f03da04579c0e6b0d6a06b4b2"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.8.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d6f6ff9a378485b298a5286656da665ba74413d36db0979633275d2e708145d4"
+
 [[package]]
 name = "resb"
 version = "0.1.2"
@@ -728,6 +888,15 @@ version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8a0d197bd2c9dc6e53b84da9556a69ba4cdfab8619eb41a8bd1cc2027a0f6b1d"
 
+[[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.228"
@@ -862,6 +1031,7 @@ version = "0.2.6"
 dependencies = [
  "calendrical_calculations",
  "core_maths",
+ "criterion",
  "iana-time-zone",
  "icu_calendar",
  "icu_locale_core",
@@ -930,6 +1100,16 @@ dependencies = [
  "zerovec",
 ]
 
+[[package]]
+name = "tinytemplate"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be4d6b5f19ff7664e8c98d03e2139cb510db9b0a60b55f8e8709b689d939b6bc"
+dependencies = [
+ "serde",
+ "serde_json",
+]
+
 [[package]]
 name = "toml"
 version = "0.8.22"
@@ -1014,6 +1194,16 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
+[[package]]
+name = "walkdir"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29790946404f91d9c5d06f9874efddea1dc06c5efe94541a7d6863108e3a5e4b"
+dependencies = [
+ "same-file",
+ "winapi-util",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.100"
@@ -1082,6 +1272,15 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "winapi-util"
+version = "0.1.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2a7b1c03c876122aa43f3020e6c3c3ee5c05081c9a00739faf7503aeba10d22"
+dependencies = [
+ "windows-sys",
+]
+
 [[package]]
 name = "windows-core"
 version = "0.61.2"
@@ -1261,6 +1460,26 @@ dependencies = [
  "synstructure",
 ]
 
+[[package]]
+name = "zerocopy"
+version = "0.8.63"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5fe1f8f1b06191a00962174c61aa5005e0bb391a6d80d07e24d115c01a92ed8"
+dependencies = [
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.8.63"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "863ad3ac83293fb4d740aedbfdc9240dd8d1a50c1099acd76ce80ce7c7230c7f"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "zerofrom"
 version = "0.1.6"
diff --git a/crates/temporal/Cargo.toml b/crates/temporal/Cargo.toml
index dde03aa05..d2c863b6a 100644
--- a/crates/temporal/Cargo.toml
+++ b/crates/temporal/Cargo.toml
@@ -37,6 +37,12 @@ calendrical_calculations = "0.2.4"
 timezone_provider = { workspace = true, features = ["zoneinfo64", "experimental_tzif"] }
 zoneinfo64 = { workspace = true }
 resb = "0.1.0"
+criterion = { version = "0.5", default-features = false, features = ["cargo_bench_support"] }
+
+[[bench]]
+name = "zoned_date_time"
+harness = false
+required-features = ["compiled_data"]
 
 [features]
 default = ["sys-local"]
diff --git a/crates/temporal/benches/zoned_date_time.rs b/crates/temporal/benches/zoned_date_time.rs
new file mode 100644
index 000000000..0736774b9
--- /dev/null
+++ b/crates/temporal/benches/zoned_date_time.rs
@@ -0,0 +1,228 @@
+//! Benchmarks for `ZonedDateTime` field access.
+//!
+//! Mirrors the harness in <https://github.com/boa-dev/temporal/issues/756>: every
+//! field getter resolves the ISO date-time from the epoch nanoseconds, so reading
+//! N fields costs N conversions. The `PlainDateTime` rows are the floor those
+//! getters should approach; the construction and arithmetic rows guard against
+//! moving that cost onto paths that never read a field.
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use temporal::options::{Disambiguation, OffsetDisambiguation};
+use temporal::TimeZone;
+use temporal::{Duration, PlainDateTime, ZonedDateTime};
+
+/// An IXDTF string carrying both an offset and an IANA annotation, which is the
+/// shape an engine actually parses.
+const SOURCE: &str = "2025-01-01T00:00:00-05:00[America/New_York]";
+
+fn parse(source: &str) -> ZonedDateTime {
+    ZonedDateTime::from_utf8(
+        source.as_bytes(),
+        Disambiguation::Compatible,
+        OffsetDisambiguation::Reject,
+    )
+    .expect("source must parse")
+}
+
+/// The step between fixtures: an uneven duration that crosses DST boundaries as
+/// the series walks forward, so the spread is not all one offset.
+fn step() -> Duration {
+    Duration::new(0, 0, 0, 11, 7, 23, 41, 0, 0, 0).expect("valid duration")
+}
+
+/// A spread of zoned date-times, parsed once and then walked forward by adding a
+/// duration, so the benchmark is not dominated by a single offset or code path.
+fn zoned_date_times() -> Vec<ZonedDateTime> {
+    let step = step();
+    let mut current = parse(SOURCE);
+    let mut out = Vec::with_capacity(64);
+    for _ in 0..64 {
+        out.push(current.clone());
+        current = current
+            .add(&step, None)
+            .expect("addition must stay in range");
+    }
+    out
+}
+
+/// Reading seven fields — the shape a formatter or `toString` takes.
+fn seven_getters(c: &mut Criterion) {
+    let zdts = zoned_date_times();
+    let pdts: Vec<PlainDateTime> = zdts.iter().map(|z| z.to_plain_date_time()).collect();
+
+    let mut group = c.benchmark_group("seven_getters");
+    group.bench_function("zoned_date_time", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                let zdt = black_box(zdt);
+                black_box((
+                    zdt.year(),
+                    zdt.month(),
+                    zdt.day(),
+                    zdt.hour(),
+                    zdt.minute(),
+                    zdt.second(),
+                    zdt.millisecond(),
+                ));
+            }
+        })
+    });
+    group.bench_function("plain_date_time", |b| {
+        b.iter(|| {
+            for pdt in &pdts {
+                let pdt = black_box(pdt);
+                black_box((
+                    pdt.year(),
+                    pdt.month(),
+                    pdt.day(),
+                    pdt.hour(),
+                    pdt.minute(),
+                    pdt.second(),
+                    pdt.millisecond(),
+                ));
+            }
+        })
+    });
+    group.bench_function("zoned_via_plain_date_time", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                let pdt = black_box(zdt).to_plain_date_time();
+                black_box((
+                    pdt.year(),
+                    pdt.month(),
+                    pdt.day(),
+                    pdt.hour(),
+                    pdt.minute(),
+                    pdt.second(),
+                    pdt.millisecond(),
+                ));
+            }
+        })
+    });
+    group.finish();
+}
+
+/// A single getter, separating the time fields (pure ISO arithmetic) from the
+/// calendar fields (which additionally build an ICU4X date).
+fn single_getter(c: &mut Criterion) {
+    let zdts = zoned_date_times();
+
+    let mut group = c.benchmark_group("single_getter");
+    group.bench_function("hour", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(black_box(zdt).hour());
+            }
+        })
+    });
+    group.bench_function("year", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(black_box(zdt).year());
+            }
+        })
+    });
+    group.finish();
+}
+
+/// Construction, which an eagerly-computed cache makes more expensive. Parsing is
+/// how an engine reaches `ZonedDateTime` from user input.
+fn construction(c: &mut Criterion) {
+    let sources = [
+        // Offset plus IANA annotation.
+        "2025-01-01T00:00:00-05:00[America/New_York]",
+        // Annotation only, so the offset is resolved from the provider.
+        "2025-07-04T12:30:45[America/New_York]",
+        // UTC designator with an annotation.
+        "2025-03-09T07:00:00Z[America/New_York]",
+        // Sub-second precision.
+        "2025-11-02T01:30:00.123456789-05:00[America/New_York]",
+    ];
+
+    let mut group = c.benchmark_group("construction");
+    group.bench_function("from_utf8", |b| {
+        b.iter(|| {
+            for source in &sources {
+                black_box(parse(black_box(source)));
+            }
+        })
+    });
+    group.finish();
+}
+
+/// Arithmetic produces a new `ZonedDateTime` without necessarily reading a field,
+/// so it is the clearest place an eager cache could regress.
+fn arithmetic(c: &mut Criterion) {
+    let zdts = zoned_date_times();
+    let step = step();
+    let day = Duration::new(0, 0, 0, 1, 0, 0, 0, 0, 0, 0).expect("valid duration");
+
+    let mut group = c.benchmark_group("arithmetic");
+    group.bench_function("add", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(black_box(zdt).add(&step, None).unwrap());
+            }
+        })
+    });
+    // Adding a day is the DST-sensitive case: the result's offset may differ from
+    // the receiver's, so the cached offset and ISO date-time must be recomputed.
+    group.bench_function("add_one_day", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(black_box(zdt).add(&day, None).unwrap());
+            }
+        })
+    });
+    // Parse, add, then read a field — the shape a caller that does real work takes,
+    // so the cache is paid for once and used once.
+    group.bench_function("parse_add_read", |b| {
+        b.iter(|| {
+            let zdt = parse(black_box(SOURCE))
+                .add(black_box(&step), None)
+                .unwrap();
+            black_box(zdt.hour())
+        })
+    });
+    group.bench_function("with_timezone", |b| {
+        let paris = TimeZone::try_from_str("Europe/Paris").expect("tz must resolve");
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(black_box(zdt).with_timezone(paris).unwrap());
+            }
+        })
+    });
+    group.finish();
+}
+
+/// String output reads every field, so it compounds the per-getter cost.
+fn to_string(c: &mut Criterion) {
+    let zdts = zoned_date_times();
+
+    c.bench_function("to_ixdtf_string", |b| {
+        b.iter(|| {
+            for zdt in &zdts {
+                black_box(
+                    black_box(zdt)
+                        .to_ixdtf_string(
+                            Default::default(),
+                            Default::default(),
+                            Default::default(),
+                            Default::default(),
+                        )
+                        .unwrap(),
+                );
+            }
+        })
+    });
+}
+
+criterion_group!(
+    benches,
+    seven_getters,
+    single_getter,
+    construction,
+    arithmetic,
+    to_string
+);
+criterion_main!(benches);
diff --git a/crates/temporal/src/builtins/core/zoned_date_time.rs b/crates/temporal/src/builtins/core/zoned_date_time.rs
index 417d83259..649d41557 100644
--- a/crates/temporal/src/builtins/core/zoned_date_time.rs
+++ b/crates/temporal/src/builtins/core/zoned_date_time.rs
@@ -257,6 +257,9 @@ pub struct ZonedDateTime {
     calendar: Calendar,
     time_zone: TimeZone,
     cached_offset: UtcOffset,
+    // We cache the IsoDateTime, because `ZonedDateTime` is immutable, and this will
+    // speed up getters.
+    cached_iso: IsoDateTime,
 }
 
 // ==== Private API ====
@@ -271,11 +274,13 @@ impl ZonedDateTime {
         calendar: Calendar,
         cached_offset: UtcOffsetSeconds,
     ) -> Self {
+        let cached_offset: UtcOffset = cached_offset.into();
         Self {
-            instant,
             calendar,
             time_zone,
-            cached_offset: cached_offset.into(),
+            cached_iso: cached_offset.get_iso_datetime_for(&instant),
+            cached_offset,
+            instant,
         }
     }
 
@@ -285,14 +290,15 @@ impl ZonedDateTime {
         calendar: Calendar,
         provider: &(impl TimeZoneProvider + ?Sized),
     ) -> TemporalResult<Self> {
-        let offset = time_zone
+        let cached_offset = time_zone
             .get_utc_offset_for(instant.epoch_nanoseconds().0, provider)
             .temporal_unwrap()?;
         Ok(Self {
-            instant,
             calendar,
             time_zone,
-            cached_offset: offset,
+            cached_iso: cached_offset.get_iso_datetime_for(&instant),
+            cached_offset,
+            instant,
         })
     }
 
@@ -300,7 +306,7 @@ impl ZonedDateTime {
     ///
     /// (which is GetISODateTimeFor(self.[[TimeZone]], self.[[EpochNanoseconds]]).)
     pub(crate) fn get_iso_datetime(&self) -> IsoDateTime {
-        self.cached_offset.get_iso_datetime_for(&self.instant)
+        self.cached_iso
     }
 
     pub(crate) fn add_zoned_date_time(