diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d1f544f2f03a..b70c7898ac077 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -88,6 +88,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Use the correct type to widen the sort fields when merging top docs ([#16881](https://github.com/opensearch-project/OpenSearch/pull/16881))
 - Limit reader writer separation to remote store enabled clusters [#16760](https://github.com/opensearch-project/OpenSearch/pull/16760)
 - Optimize innerhits query performance [#16937](https://github.com/opensearch-project/OpenSearch/pull/16937)
+- Increase force merge threads to 1/8th of cores [#17255](https://github.com/opensearch-project/OpenSearch/pull/17255)
 
 ### Deprecated
 - Performing update operation with default pipeline or final pipeline is deprecated ([#16712](https://github.com/opensearch-project/OpenSearch/pull/16712))
diff --git a/server/src/main/java/org/opensearch/threadpool/ThreadPool.java b/server/src/main/java/org/opensearch/threadpool/ThreadPool.java
index 59d3b110aeca8..b67b00bb42054 100644
--- a/server/src/main/java/org/opensearch/threadpool/ThreadPool.java
+++ b/server/src/main/java/org/opensearch/threadpool/ThreadPool.java
@@ -278,7 +278,10 @@ public ThreadPool(
             Names.FETCH_SHARD_STARTED,
             new ScalingExecutorBuilder(Names.FETCH_SHARD_STARTED, 1, 2 * allocatedProcessors, TimeValue.timeValueMinutes(5))
         );
-        builders.put(Names.FORCE_MERGE, new FixedExecutorBuilder(settings, Names.FORCE_MERGE, 1, -1));
+        builders.put(
+            Names.FORCE_MERGE,
+            new FixedExecutorBuilder(settings, Names.FORCE_MERGE, oneEighthAllocatedProcessors(allocatedProcessors), -1)
+        );
         builders.put(
             Names.FETCH_SHARD_STORE,
             new ScalingExecutorBuilder(Names.FETCH_SHARD_STORE, 1, 2 * allocatedProcessors, TimeValue.timeValueMinutes(5))
@@ -678,6 +681,10 @@ static int boundedBy(int value, int min, int max) {
         return Math.min(max, Math.max(min, value));
     }
 
+    static int oneEighthAllocatedProcessors(final int allocatedProcessors) {
+        return boundedBy(allocatedProcessors / 8, 1, Integer.MAX_VALUE);
+    }
+
     static int halfAllocatedProcessors(int allocatedProcessors) {
         return (allocatedProcessors + 1) / 2;
     }
diff --git a/server/src/test/java/org/opensearch/threadpool/ThreadPoolTests.java b/server/src/test/java/org/opensearch/threadpool/ThreadPoolTests.java
index 205bf7621c576..fd79115ad5872 100644
--- a/server/src/test/java/org/opensearch/threadpool/ThreadPoolTests.java
+++ b/server/src/test/java/org/opensearch/threadpool/ThreadPoolTests.java
@@ -196,4 +196,12 @@ public void testThreadPoolResizeFail() {
             terminate(threadPool);
         }
     }
+
+    public void testOneEighthAllocatedProcessors() {
+        assertThat(ThreadPool.oneEighthAllocatedProcessors(1), equalTo(1));
+        assertThat(ThreadPool.oneEighthAllocatedProcessors(4), equalTo(1));
+        assertThat(ThreadPool.oneEighthAllocatedProcessors(8), equalTo(1));
+        assertThat(ThreadPool.oneEighthAllocatedProcessors(32), equalTo(4));
+        assertThat(ThreadPool.oneEighthAllocatedProcessors(128), equalTo(16));
+    }
 }