diff --git a/CHANGELOG.md b/CHANGELOG.md
index fab7315b4..af942bd4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 - Added new functions: VSTACK, HSTACK. [#1698](https://github.com/handsontable/hyperformula/pull/1698)
 - Added a new function: `XIRR`. [#1701](https://github.com/handsontable/hyperformula/pull/1701)
+- Added the UNIQUE function. [#1708](https://github.com/handsontable/hyperformula/pull/1708)
 - Added the SORT function. [#1707](https://github.com/handsontable/hyperformula/pull/1707)
 - Added an Indonesian (Bahasa Indonesia) language pack. [#1674](https://github.com/handsontable/hyperformula/pull/1674)
 - Added a `stringifyCurrency` config option that lets you plug in a custom currency formatter for the `TEXT` function. [#1145](https://github.com/handsontable/hyperformula/issues/1145)
diff --git a/docs/guide/built-in-functions.md b/docs/guide/built-in-functions.md
index a322bca16..51846e097 100644
--- a/docs/guide/built-in-functions.md
+++ b/docs/guide/built-in-functions.md
@@ -67,6 +67,7 @@ Total number of functions: **{{ $page.functionsCount }}**
 | SEQUENCE        | Returns an array of sequential numbers.                          | SEQUENCE(Rows, [Cols], [Start], [Step])                    |
 | VSTACK          | Stacks arrays vertically into a single array.                    | VSTACK(Array1, [Array2], ...[ArrayN])                      |
 | HSTACK          | Stacks arrays horizontally into a single array.                  | HSTACK(Array1, [Array2], ...[ArrayN])                      |
+| UNIQUE          | Returns the unique rows or columns of an array.                  | UNIQUE(Array, [ByCol], [ExactlyOnce])                      |
 | SORT            | Sorts the rows or columns of an array.                           | SORT(Array, [SortIndex], [SortOrder], [ByCol])             |
 
 ### Date and time
diff --git a/docs/guide/known-limitations.md b/docs/guide/known-limitations.md
index 76a56c3d7..7f0e2361d 100644
--- a/docs/guide/known-limitations.md
+++ b/docs/guide/known-limitations.md
@@ -38,6 +38,11 @@ a circular reference.
 * Array-producing functions (e.g., SEQUENCE, FILTER) require their output dimensions to be determinable at parse time. Passing cell references or formulas as dimension arguments (e.g., `=SEQUENCE(A1)`) results in a `#VALUE!` error, because the output size cannot be resolved before evaluation.
 * The TEXT function does not accept embedded double-quote literals in the format string. In Excel, `""` inside a format string is an escape sequence for a literal `"` character — e.g. `=TEXT(1234.5, "#,##0.00 ""zł""")` returns `"1,234.50 zł"`. If your application requires this escape sequence, supply a custom [`stringifyCurrency`](currency-handling.md) callback.
 
+### UNIQUE function
+
+* Comparison of values follows HyperFormula's own equality rules, which honor the `caseSensitive` and `accentSensitive` configuration options. By default comparison is case-insensitive.
+
+* When `ExactlyOnce` is TRUE and no row or column occurs exactly once, `UNIQUE` returns a `#N/A` error (the result would otherwise be empty).
 ### SORT function
 
 * The `SortIndex` argument accepts a single key only. Multi-key sorting through an array constant (for example `=SORT(A1:B9, {1,2})`) is not supported; sort by one column or row at a time.
diff --git a/src/i18n/languages/csCZ.ts b/src/i18n/languages/csCZ.ts
index 9e035a881..830b1c196 100644
--- a/src/i18n/languages/csCZ.ts
+++ b/src/i18n/languages/csCZ.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'USEKNOUT',
     UNICHAR: 'UNICHAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIQUE',
     UPPER: 'VELKÁ',
     VALUE: 'HODNOTA',
     VARA: 'VARA',
diff --git a/src/i18n/languages/daDK.ts b/src/i18n/languages/daDK.ts
index 6a9e78f7d..90296fd42 100644
--- a/src/i18n/languages/daDK.ts
+++ b/src/i18n/languages/daDK.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'AFKORT',
     UNICHAR: 'UNICHAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'ENTYDIGE',
     UPPER: 'STORE.BOGSTAVER',
     VALUE: 'VÆRDI',
     VARA: 'VARIANSV',
diff --git a/src/i18n/languages/deDE.ts b/src/i18n/languages/deDE.ts
index 1becb9679..daaaa0bf7 100644
--- a/src/i18n/languages/deDE.ts
+++ b/src/i18n/languages/deDE.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'KÜRZEN',
     UNICHAR: 'UNIZEICHEN',
     UNICODE: 'UNICODE',
+    UNIQUE: 'EINDEUTIG',
     UPPER: 'GROSS',
     VALUE: 'WERT',
     VARA: 'VARIANZA',
diff --git a/src/i18n/languages/enGB.ts b/src/i18n/languages/enGB.ts
index 0350eb314..d271b732c 100644
--- a/src/i18n/languages/enGB.ts
+++ b/src/i18n/languages/enGB.ts
@@ -243,6 +243,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'TRUNC',
     UNICHAR: 'UNICHAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIQUE',
     UPPER: 'UPPER',
     VALUE: 'VALUE',
     VARA: 'VARA',
diff --git a/src/i18n/languages/esES.ts b/src/i18n/languages/esES.ts
index f446ad063..6fea52e4e 100644
--- a/src/i18n/languages/esES.ts
+++ b/src/i18n/languages/esES.ts
@@ -241,6 +241,7 @@ export const dictionary: RawTranslationPackage = {
     TRUNC: 'TRUNCAR',
     UNICHAR: 'UNICHAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNICOS',
     UPPER: 'MAYUSC',
     VALUE: 'VALOR',
     VARA: 'VARA',
diff --git a/src/i18n/languages/fiFI.ts b/src/i18n/languages/fiFI.ts
index 554b12e33..a3b319af2 100644
--- a/src/i18n/languages/fiFI.ts
+++ b/src/i18n/languages/fiFI.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'KATKAISE',
     UNICHAR: 'UNICODEMERKKI',
     UNICODE: 'UNICODE',
+    UNIQUE: 'AINUTKERTAISET.ARVOT',
     UPPER: 'ISOT',
     VALUE: 'ARVO',
     VARA: 'VARA',
diff --git a/src/i18n/languages/frFR.ts b/src/i18n/languages/frFR.ts
index 81bcdd779..a29109053 100644
--- a/src/i18n/languages/frFR.ts
+++ b/src/i18n/languages/frFR.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'TRONQUE',
     UNICHAR: 'UNICAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIQUE',
     UPPER: 'MAJUSCULE',
     VALUE: 'CNUM',
     VARA: 'VARA',
diff --git a/src/i18n/languages/huHU.ts b/src/i18n/languages/huHU.ts
index 4d429523a..fafc2c4b9 100644
--- a/src/i18n/languages/huHU.ts
+++ b/src/i18n/languages/huHU.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'CSONK',
     UNICHAR: 'UNIKARAKTER',
     UNICODE: 'UNICODE',
+    UNIQUE: 'EGYEDI',
     UPPER: 'NAGYBETŰS',
     VALUE: 'ÉRTÉK',
     VARA: 'VARA',
diff --git a/src/i18n/languages/idID.ts b/src/i18n/languages/idID.ts
index e5c8723cb..719cb11db 100644
--- a/src/i18n/languages/idID.ts
+++ b/src/i18n/languages/idID.ts
@@ -243,6 +243,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'POTONG',
     UNICHAR: 'UNIKARAKTER',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIQUE',
     UPPER: 'HURUF.BESAR',
     VALUE: 'NILAI',
     VARA: 'VARA',
diff --git a/src/i18n/languages/itIT.ts b/src/i18n/languages/itIT.ts
index 210047149..40ec9cf41 100644
--- a/src/i18n/languages/itIT.ts
+++ b/src/i18n/languages/itIT.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'TRONCA',
     UNICHAR: 'CARATT.UNI',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNICI',
     UPPER: 'MAIUSC',
     VALUE: 'VALORE',
     VARA: 'VAR.VALORI',
diff --git a/src/i18n/languages/nbNO.ts b/src/i18n/languages/nbNO.ts
index fcfa50c8f..89c0f85f7 100644
--- a/src/i18n/languages/nbNO.ts
+++ b/src/i18n/languages/nbNO.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'AVKORT',
     UNICHAR: 'UNICODETEGN',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIK',
     UPPER: 'STORE',
     VALUE: 'VERDI',
     VARA: 'VARIANSA',
diff --git a/src/i18n/languages/nlNL.ts b/src/i18n/languages/nlNL.ts
index fcc0640c4..73ef99687 100644
--- a/src/i18n/languages/nlNL.ts
+++ b/src/i18n/languages/nlNL.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'GEHEEL',
     UNICHAR: 'UNITEKEN',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIEK',
     UPPER: 'HOOFDLETTERS',
     VALUE: 'WAARDE',
     VARA: 'VARA',
diff --git a/src/i18n/languages/plPL.ts b/src/i18n/languages/plPL.ts
index 8b42176d3..003b0fd64 100644
--- a/src/i18n/languages/plPL.ts
+++ b/src/i18n/languages/plPL.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'LICZBA.CAŁK',
     UNICHAR: 'ZNAK.UNICODE',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIKATOWE',
     UPPER: 'LITERY.WIELKIE',
     VALUE: 'WARTOŚĆ',
     VARA: 'WARIANCJA.A',
diff --git a/src/i18n/languages/ptPT.ts b/src/i18n/languages/ptPT.ts
index 1d478543a..408d7f772 100644
--- a/src/i18n/languages/ptPT.ts
+++ b/src/i18n/languages/ptPT.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'TRUNCAR',
     UNICHAR: 'CARACTUNI',
     UNICODE: 'UNICODE',
+    UNIQUE: 'EXCLUSIVOS',
     UPPER: 'MAIÚSCULA',
     VALUE: 'VALOR',
     VARA: 'VARA',
diff --git a/src/i18n/languages/ruRU.ts b/src/i18n/languages/ruRU.ts
index 856d94083..657b0db37 100644
--- a/src/i18n/languages/ruRU.ts
+++ b/src/i18n/languages/ruRU.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'ОТБР',
     UNICHAR: 'ЮНИСИМВ',
     UNICODE: 'UNICODE',
+    UNIQUE: 'УНИК',
     UPPER: 'ПРОПИСН',
     VALUE: 'ЗНАЧ',
     VARA: 'ДИСПА',
diff --git a/src/i18n/languages/svSE.ts b/src/i18n/languages/svSE.ts
index ad27924ee..5f8758008 100644
--- a/src/i18n/languages/svSE.ts
+++ b/src/i18n/languages/svSE.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'AVKORTA',
     UNICHAR: 'UNICHAR',
     UNICODE: 'UNICODE',
+    UNIQUE: 'UNIK',
     UPPER: 'VERSALER',
     VALUE: 'TEXTNUM',
     VARA: 'VARA',
diff --git a/src/i18n/languages/trTR.ts b/src/i18n/languages/trTR.ts
index c19796ed6..dc243600d 100644
--- a/src/i18n/languages/trTR.ts
+++ b/src/i18n/languages/trTR.ts
@@ -241,6 +241,7 @@ const dictionary: RawTranslationPackage = {
     TRUNC: 'NSAT',
     UNICHAR: 'UNICODEKARAKTERİ',
     UNICODE: 'UNICODE',
+    UNIQUE: 'BENZERSİZ',
     UPPER: 'BÜYÜKHARF',
     VALUE: 'DEĞER',
     VARA: 'VARA',
diff --git a/src/interpreter/plugin/UniquePlugin.ts b/src/interpreter/plugin/UniquePlugin.ts
new file mode 100644
index 000000000..5db1fb510
--- /dev/null
+++ b/src/interpreter/plugin/UniquePlugin.ts
@@ -0,0 +1,157 @@
+/**
+ * @license
+ * Copyright (c) 2025 Handsoncode. All rights reserved.
+ */
+
+import {ArraySize} from '../../ArraySize'
+import {CellError, ErrorType} from '../../Cell'
+import {ErrorMessage} from '../../error-message'
+import {ProcedureAst} from '../../parser'
+import {InterpreterState} from '../InterpreterState'
+import {InternalNoErrorScalarValue, InternalScalarValue, InterpreterValue} from '../InterpreterValue'
+import {SimpleRangeValue} from '../../SimpleRangeValue'
+import {FunctionArgumentType, FunctionPlugin, FunctionPluginTypecheck, ImplementedFunctions} from './FunctionPlugin'
+
+/**
+ * Plugin implementing the UNIQUE spreadsheet function.
+ *
+ * UNIQUE(array, [by_col], [exactly_once]) returns the distinct rows (or columns
+ * when by_col is TRUE) of `array`, preserving first-occurrence order. When
+ * exactly_once is TRUE, only rows/columns that occur exactly once are returned.
+ * Equality delegates to {@link ArithmeticHelper}, so comparison honors the
+ * caseSensitive/accentSensitive configuration (case-insensitive by default).
+ */
+export class UniquePlugin extends FunctionPlugin implements FunctionPluginTypecheck<UniquePlugin> {
+  public static implementedFunctions: ImplementedFunctions = {
+    'UNIQUE': {
+      method: 'unique',
+      sizeOfResultArrayMethod: 'uniqueArraySize',
+      enableArrayArithmeticForArguments: true,
+      parameters: [
+        {argumentType: FunctionArgumentType.RANGE},
+        {argumentType: FunctionArgumentType.BOOLEAN, defaultValue: false, emptyAsDefault: true},
+        {argumentType: FunctionArgumentType.BOOLEAN, defaultValue: false, emptyAsDefault: true},
+      ],
+      vectorizationForbidden: true,
+    },
+  }
+
+  /**
+   * Corresponds to UNIQUE(array, [by_col], [exactly_once]).
+   *
+   * Errors found anywhere in the input range are propagated. An empty result
+   * (only reachable via exactly_once when nothing occurs exactly once) yields
+   * #N/A, mirroring FILTER's empty-result handling.
+   *
+   * @param {ProcedureAst} ast - the parsed function-call AST node.
+   * @param {InterpreterState} state - current interpreter evaluation state.
+   */
+  public unique(ast: ProcedureAst, state: InterpreterState): InterpreterValue {
+    return this.runFunction(ast.args, state, this.metadata('UNIQUE'),
+      (range: SimpleRangeValue, byCol: boolean, exactlyOnce: boolean) => {
+        const data = range.data
+
+        const firstError = UniquePlugin.findFirstError(data)
+        if (firstError !== undefined) {
+          return firstError
+        }
+
+        // Work in "vectors": rows for the default, columns when by_col is TRUE.
+        const vectors: InternalScalarValue[][] = byCol
+          ? UniquePlugin.transpose(data)
+          : data.map(row => row.slice())
+
+        const equalVectors = (v1: InternalScalarValue[], v2: InternalScalarValue[]): boolean => {
+          // v1 and v2 are always the same length here: they are rows (or columns,
+          // after transpose) of the same rectangular range, so no length check is
+          // needed before the element-wise comparison.
+          for (let i = 0; i < v1.length; i++) {
+            if (!this.arithmeticHelper.eq(v1[i] as InternalNoErrorScalarValue, v2[i] as InternalNoErrorScalarValue)) {
+              return false
+            }
+          }
+          return true
+        }
+
+        // Preserve first-occurrence order; count occurrences for exactly_once.
+        // Deduplication is O(n^2) in the number of vectors: equality is locale-aware
+        // (via arithmeticHelper.eq) and not trivially hashable, so each vector is
+        // compared against the distinct ones found so far. This matches Excel's
+        // observable behavior; for very large inputs it is the known cost.
+        const distinct: InternalScalarValue[][] = []
+        const counts: number[] = []
+        for (const vector of vectors) {
+          const existing = distinct.findIndex(d => equalVectors(d, vector))
+          if (existing === -1) {
+            distinct.push(vector)
+            counts.push(1)
+          } else {
+            counts[existing] += 1
+          }
+        }
+
+        const kept = exactlyOnce
+          ? distinct.filter((_, i) => counts[i] === 1)
+          : distinct
+
+        if (kept.length === 0) {
+          return new CellError(ErrorType.NA, ErrorMessage.EmptyRange)
+        }
+
+        const result = byCol ? UniquePlugin.transpose(kept) : kept
+        return SimpleRangeValue.onlyValues(result)
+      }
+    )
+  }
+
+  /**
+   * Predicts the output array size for UNIQUE at parse time.
+   * The size is data-dependent, so we predict the input size as an upper bound
+   * (mirroring FILTER) and return the smaller actual result at runtime. A fresh
+   * ArraySize is returned so the input's `isRef` flag is not propagated (an
+   * ArraySize flagged as a ref is treated as scalar, which would collapse the
+   * spilled result into a single cell).
+   *
+   * @param {ProcedureAst} ast - the parsed function-call AST node.
+   * @param {InterpreterState} state - current interpreter evaluation state.
+   */
+  public uniqueArraySize(ast: ProcedureAst, state: InterpreterState): ArraySize {
+    if (ast.args.length < 1 || ast.args.length > 3) {
+      return ArraySize.error()
+    }
+    const metadata = this.metadata('UNIQUE')
+    const subChecks = ast.args.map((arg) =>
+      this.arraySizeForAst(arg, new InterpreterState(state.formulaAddress, state.arraysFlag || (metadata?.enableArrayArithmeticForArguments ?? false))))
+    return new ArraySize(subChecks[0].width, subChecks[0].height)
+  }
+
+  /** Returns the first {@link CellError} found in a 2-D array, or undefined. */
+  private static findFirstError(data: InternalScalarValue[][]): CellError | undefined {
+    for (const row of data) {
+      for (const cell of row) {
+        if (cell instanceof CellError) {
+          return cell
+        }
+      }
+    }
+    return undefined
+  }
+
+  /** Transposes a 2-D array (rows <-> columns). */
+  private static transpose(data: InternalScalarValue[][]): InternalScalarValue[][] {
+    if (data.length === 0) {
+      return []
+    }
+    const height = data.length
+    const width = data[0].length
+    const result: InternalScalarValue[][] = []
+    for (let c = 0; c < width; c++) {
+      const col: InternalScalarValue[] = []
+      for (let r = 0; r < height; r++) {
+        col.push(data[r][c])
+      }
+      result.push(col)
+    }
+    return result
+  }
+}
diff --git a/src/interpreter/plugin/index.ts b/src/interpreter/plugin/index.ts
index a390ad843..2a3005375 100644
--- a/src/interpreter/plugin/index.ts
+++ b/src/interpreter/plugin/index.ts
@@ -36,6 +36,7 @@ export {RadiansPlugin} from './RadiansPlugin'
 export {RadixConversionPlugin} from './RadixConversionPlugin'
 export {RandomPlugin} from './RandomPlugin'
 export {SequencePlugin} from './SequencePlugin'
+export {UniquePlugin} from './UniquePlugin'
 export {SortPlugin} from './SortPlugin'
 export {RoundingPlugin} from './RoundingPlugin'
 export {SqrtPlugin} from './SqrtPlugin'