diff --git a/changelog/unreleased/SOLR-5505-infostream-core-name.yml b/changelog/unreleased/SOLR-5505-infostream-core-name.yml
new file mode 100644
index 000000000000..4d4ed26a7b58
--- /dev/null
+++ b/changelog/unreleased/SOLR-5505-infostream-core-name.yml
@@ -0,0 +1,7 @@
+title: "LoggingInfoStream (IndexWriter infoStream logging) now includes the core name in every message so multi-core logs can be told apart"
+type: changed
+authors:
+  - name: Nick Shanin
+links:
+  - name: SOLR-5505
+    url: https://issues.apache.org/jira/browse/SOLR-5505
diff --git a/solr/core/src/java/org/apache/solr/update/LoggingInfoStream.java b/solr/core/src/java/org/apache/solr/update/LoggingInfoStream.java
index 69bb4c12cb1a..6197833f928b 100644
--- a/solr/core/src/java/org/apache/solr/update/LoggingInfoStream.java
+++ b/solr/core/src/java/org/apache/solr/update/LoggingInfoStream.java
@@ -26,10 +26,27 @@
 public class LoggingInfoStream extends InfoStream {
   private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
+  private final String coreName;
+
+  public LoggingInfoStream() {
+    this(null);
+  }
+
+  /**
+   * @param coreName if not null, the name of the core is added to every message
+   */
+  public LoggingInfoStream(String coreName) {
+    this.coreName = coreName;
+  }
+
   @Override
   public void message(String component, String message) {
-    if (log.isInfoEnabled()) {
-      log.info("[{}][{}]: {}", component, Thread.currentThread().getName(), message);
+    if (coreName == null) {
+      if (log.isInfoEnabled()) {
+        log.info("[{}][{}]: {}", component, Thread.currentThread().getName(), message);
+      }
+    } else if (log.isInfoEnabled()) {
+      log.info("[{}][{}][{}]: {}", coreName, component, Thread.currentThread().getName(), message);
     }
   }
 
diff --git a/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java b/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java
index 70330b89c71d..d983a8e566a8 100644
--- a/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java
+++ b/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java
@@ -258,7 +258,11 @@ public IndexWriterConfig toIndexWriterConfig(SolrCore core) throws IOException {
     iwc.setMergePolicy(mergePolicy);
     MergeScheduler mergeScheduler = buildMergeScheduler(core.getResourceLoader());
     iwc.setMergeScheduler(mergeScheduler);
-    iwc.setInfoStream(infoStream);
+    // one config is shared by reloads and may not know its core, so tag the stream per core here
+    iwc.setInfoStream(
+        infoStream instanceof LoggingInfoStream
+            ? new LoggingInfoStream(core.getName())
+            : infoStream);
 
     if (mergePolicy instanceof SortingMergePolicy) {
       Sort indexSort = ((SortingMergePolicy) mergePolicy).getSort();
diff --git a/solr/core/src/test/org/apache/solr/core/TestInfoStreamLogging.java b/solr/core/src/test/org/apache/solr/core/TestInfoStreamLogging.java
index 3e031e1847f8..9c76fbe29ee0 100644
--- a/solr/core/src/test/org/apache/solr/core/TestInfoStreamLogging.java
+++ b/solr/core/src/test/org/apache/solr/core/TestInfoStreamLogging.java
@@ -16,9 +16,12 @@
  */
 package org.apache.solr.core;
 
+import static org.hamcrest.Matchers.containsString;
+
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.update.LoggingInfoStream;
+import org.apache.solr.util.LogListener;
 import org.junit.BeforeClass;
 
 public class TestInfoStreamLogging extends SolrTestCaseJ4 {
@@ -33,4 +36,13 @@ public void testIndexConfig() throws Exception {
 
     assertTrue(iwc.getInfoStream() instanceof LoggingInfoStream);
   }
+
+  public void testMessagesNameTheCore() throws Exception {
+    IndexWriterConfig iwc = solrConfig.indexConfig.toIndexWriterConfig(h.getCore());
+
+    try (LogListener listener = LogListener.info(LoggingInfoStream.class)) {
+      iwc.getInfoStream().message("IW", "hello from the stream");
+      assertThat(listener.pollMessage(), containsString("[" + h.getCore().getName() + "][IW]"));
+    }
+  }
 }