diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index c6e6f130b23..2cc9710527b 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -126,6 +126,9 @@ New Features
 
 * SOLR-14604: Add the ability to uninstall a package from with the Package CLI. (MarcusSorealheis)
 
+* SOLR-14582: Expose IWC.setMaxCommitMergeWaitMillis in Solr's index config. This is an expert config option that can be
+  set when using a custom MergePolicy (doesn't have any effect on the default MP) (Tomás Fernández Löbbe)
+
 Improvements
 ---------------------
 
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 e189ad16b46..50bda0ef67f 100644
--- a/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java
+++ b/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java
@@ -68,6 +68,19 @@ public class SolrIndexConfig implements MapSerializable {
 
   public final double ramBufferSizeMB;
   public final int ramPerThreadHardLimitMB;
+  /**
+   * <p>
+   * When using a custom merge policy that allows triggering synchronous merges on commit
+   * (see {@link MergePolicy#findFullFlushMerges(org.apache.lucene.index.MergeTrigger, org.apache.lucene.index.SegmentInfos, org.apache.lucene.index.MergePolicy.MergeContext)}),
+   * a timeout (in milliseconds) can be set for those merges to finish. Use {@code <maxCommitMergeWaitTime>1000</maxCommitMergeWaitTime>} in the {@code <indexConfig>} section.
+   * See {@link IndexWriterConfig#setMaxCommitMergeWaitMillis(long)}.
+   * </p>
+   * <p>
+   * Note that as of Solr 8.6, no {@code MergePolicy} shipped with Lucene/Solr make use of
+   * {@code MergePolicy.findFullFlushMerges}, which means this setting has no effect unless a custom {@code MergePolicy} is used.
+   * </p> 
+   */
+  public final int maxCommitMergeWaitMillis;
 
   public final int writeLockTimeout;
   public final String lockType;
@@ -87,6 +100,7 @@ public class SolrIndexConfig implements MapSerializable {
     maxBufferedDocs = -1;
     ramBufferSizeMB = 100;
     ramPerThreadHardLimitMB = -1;
+    maxCommitMergeWaitMillis = -1;
     writeLockTimeout = -1;
     lockType = DirectoryFactory.LOCK_TYPE_NATIVE;
     mergePolicyFactoryInfo = null;
@@ -129,8 +143,9 @@ public class SolrIndexConfig implements MapSerializable {
         true);
 
     useCompoundFile = solrConfig.getBool(prefix+"/useCompoundFile", def.useCompoundFile);
-    maxBufferedDocs=solrConfig.getInt(prefix+"/maxBufferedDocs",def.maxBufferedDocs);
+    maxBufferedDocs = solrConfig.getInt(prefix+"/maxBufferedDocs", def.maxBufferedDocs);
     ramBufferSizeMB = solrConfig.getDouble(prefix+"/ramBufferSizeMB", def.ramBufferSizeMB);
+    maxCommitMergeWaitMillis = solrConfig.getInt(prefix+"/maxCommitMergeWaitTime", def.maxCommitMergeWaitMillis);
 
     // how do we validate the value??
     ramPerThreadHardLimitMB = solrConfig.getInt(prefix+"/ramPerThreadHardLimitMB", def.ramPerThreadHardLimitMB);
@@ -185,6 +200,7 @@ public class SolrIndexConfig implements MapSerializable {
         "maxBufferedDocs", maxBufferedDocs,
         "ramBufferSizeMB", ramBufferSizeMB,
         "ramPerThreadHardLimitMB", ramPerThreadHardLimitMB,
+        "maxCommitMergeWaitTime", maxCommitMergeWaitMillis,
         "writeLockTimeout", writeLockTimeout,
         "lockType", lockType,
         "infoStreamEnabled", infoStream != InfoStream.NO_OUTPUT);
@@ -230,6 +246,10 @@ public class SolrIndexConfig implements MapSerializable {
     if (ramPerThreadHardLimitMB != -1) {
       iwc.setRAMPerThreadHardLimitMB(ramPerThreadHardLimitMB);
     }
+    
+    if (maxCommitMergeWaitMillis > 0) {
+      iwc.setMaxCommitMergeWaitMillis(maxCommitMergeWaitMillis);
+    }
 
     iwc.setSimilarity(schema.getSimilarity());
     MergePolicy mergePolicy = buildMergePolicy(core.getResourceLoader(), schema);
diff --git a/solr/core/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml b/solr/core/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml
index 20ddf96df42..de5c714aa23 100644
--- a/solr/core/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml
+++ b/solr/core/src/test-files/solr/collection1/conf/solrconfig.snippet.randomindexconfig.xml
@@ -32,6 +32,7 @@ A solrconfig.xml snippet containing indexConfig settings for randomized testing.
 
   <maxBufferedDocs>${solr.tests.maxBufferedDocs}</maxBufferedDocs>
   <ramBufferSizeMB>${solr.tests.ramBufferSizeMB}</ramBufferSizeMB>
+  <maxCommitMergeWaitTime>${solr.tests.maxCommitMergeWaitTime:-1}</maxCommitMergeWaitTime>
   <ramPerThreadHardLimitMB>${solr.tests.ramPerThreadHardLimitMB}</ramPerThreadHardLimitMB>
 
   <mergeScheduler class="${solr.tests.mergeScheduler}" />
diff --git a/solr/core/src/test/org/apache/solr/update/SolrIndexConfigTest.java b/solr/core/src/test/org/apache/solr/update/SolrIndexConfigTest.java
index 5ae02aff2d2..2e4e59759c1 100644
--- a/solr/core/src/test/org/apache/solr/update/SolrIndexConfigTest.java
+++ b/solr/core/src/test/org/apache/solr/update/SolrIndexConfigTest.java
@@ -36,6 +36,7 @@ import org.apache.solr.core.TestMergePolicyConfig;
 import org.apache.solr.index.SortingMergePolicy;
 import org.apache.solr.schema.IndexSchema;
 import org.apache.solr.schema.IndexSchemaFactory;
+import org.junit.After;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
@@ -58,6 +59,12 @@ public class SolrIndexConfigTest extends SolrTestCaseJ4 {
     initCore(solrConfigFileName,schemaFileName);
   }
   
+  @After
+  public void tearDown() throws Exception {
+    System.clearProperty("solr.tests.maxCommitMergeWait");
+    super.tearDown();
+  }
+  
   private final Path instanceDir = TEST_PATH().resolve("collection1");
 
   @Test
@@ -177,6 +184,8 @@ public class SolrIndexConfigTest extends SolrTestCaseJ4 {
     ++mSizeExpected; assertTrue(m.get("maxBufferedDocs") instanceof Integer);
 
     ++mSizeExpected; assertTrue(m.get("ramBufferSizeMB") instanceof Double);
+    
+    ++mSizeExpected; assertTrue(m.get("maxCommitMergeWaitTime") instanceof Integer);
 
     ++mSizeExpected; assertTrue(m.get("ramPerThreadHardLimitMB") instanceof Integer);
 
@@ -208,4 +217,14 @@ public class SolrIndexConfigTest extends SolrTestCaseJ4 {
 
     assertEquals(mSizeExpected, m.size());
   }
+  
+  public void testMaxCommitMergeWaitTime() throws Exception {
+    SolrConfig sc = new SolrConfig(TEST_PATH().resolve("collection1"), "solrconfig-test-misc.xml");
+    assertEquals(-1, sc.indexConfig.maxCommitMergeWaitMillis);
+    assertEquals(IndexWriterConfig.DEFAULT_MAX_COMMIT_MERGE_WAIT_MILLIS, sc.indexConfig.toIndexWriterConfig(h.getCore()).getMaxCommitMergeWaitMillis());
+    System.setProperty("solr.tests.maxCommitMergeWaitTime", "10");
+    sc = new SolrConfig(TEST_PATH().resolve("collection1"), "solrconfig-test-misc.xml");
+    assertEquals(10, sc.indexConfig.maxCommitMergeWaitMillis);
+    assertEquals(10, sc.indexConfig.toIndexWriterConfig(h.getCore()).getMaxCommitMergeWaitMillis());
+  }
 }