diff --git a/core/src/main/scala/org/apache/spark/executor/Executor.scala b/core/src/main/scala/org/apache/spark/executor/Executor.scala
index 3edba45ef89f..68c38fb6179f 100644
--- a/core/src/main/scala/org/apache/spark/executor/Executor.scala
+++ b/core/src/main/scala/org/apache/spark/executor/Executor.scala
@@ -95,6 +95,13 @@ private[spark] class Executor(
 
   private[executor] val conf = env.conf
 
+  // SPARK-48131: Unify MDC key mdc.taskName and task_name in Spark 4.0 release.
+  private[executor] val taskNameMDCKey = if (conf.get(LEGACY_TASK_NAME_MDC_ENABLED)) {
+    "mdc.taskName"
+  } else {
+    LogKeys.TASK_NAME.name
+  }
+
   // SPARK-40235: updateDependencies() uses a ReentrantLock instead of the `synchronized` keyword
   // so that tasks can exit quickly if they are interrupted while waiting on another task to
   // finish downloading dependencies.
@@ -914,7 +921,7 @@ private[spark] class Executor(
     try {
       mdc.foreach { case (key, value) => MDC.put(key, value) }
       // avoid overriding the takName by the user
-      MDC.put(LogKeys.TASK_NAME.name, taskName)
+      MDC.put(taskNameMDCKey, taskName)
     } catch {
       case _: NoSuchFieldError => logInfo("MDC is not supported.")
     }
@@ -923,7 +930,7 @@ private[spark] class Executor(
   private def cleanMDCForTask(taskName: String, mdc: Seq[(String, String)]): Unit = {
     try {
       mdc.foreach { case (key, _) => MDC.remove(key) }
-      MDC.remove(LogKeys.TASK_NAME.name)
+      MDC.remove(taskNameMDCKey)
     } catch {
       case _: NoSuchFieldError => logInfo("MDC is not supported.")
     }
diff --git a/core/src/main/scala/org/apache/spark/internal/config/package.scala b/core/src/main/scala/org/apache/spark/internal/config/package.scala
index 2e207422ae06..d11e9fdea0f3 100644
--- a/core/src/main/scala/org/apache/spark/internal/config/package.scala
+++ b/core/src/main/scala/org/apache/spark/internal/config/package.scala
@@ -151,6 +151,16 @@ package object config {
       .booleanConf
       .createWithDefault(true)
 
+  private[spark] val LEGACY_TASK_NAME_MDC_ENABLED =
+    ConfigBuilder("spark.log.legacyTaskNameMdc.enabled")
+      .doc("When true, the MDC (Mapped Diagnostic Context) key `mdc.taskName` will be set in the " +
+        "log output, which is the behavior of Spark version 3.1 through Spark 3.5 releases. " +
+        "When false, the logging framework will use `task_name` as the MDC key, " +
+        "aligning it with the naming convention of newer MDC keys introduced in Spark 4.0 release.")
+      .version("4.0.0")
+      .booleanConf
+      .createWithDefault(false)
+
   private[spark] val DRIVER_LOG_LOCAL_DIR =
     ConfigBuilder("spark.driver.log.localDir")
       .doc("Specifies a local directory to write driver logs and enable Driver Log UI Tab.")
diff --git a/docs/core-migration-guide.md b/docs/core-migration-guide.md
index 597900630b3f..00a6690492ea 100644
--- a/docs/core-migration-guide.md
+++ b/docs/core-migration-guide.md
@@ -44,6 +44,8 @@ license: |
 
 - Since Spark 4.0, the default log4j output of `spark-submit` has shifted from plain text to JSON lines to enhance analyzability. To revert to plain text output, you can rename the file `conf/log4j2.properties.pattern-layout-template` as `conf/log4j2.properties`, or use a custom log4j configuration file.
 
+- Since Spark 4.0, the MDC (Mapped Diagnostic Context) key for Spark task names in Spark logs has been changed from `mdc.taskName` to `task_name`. To use the key `mdc.taskName`, you can set `spark.log.legacyTaskNameMdc.enabled` to `true`.
+
 - Since Spark 4.0, Spark performs speculative executions less agressively with `spark.speculation.multiplier=3` and `spark.speculation.quantile=0.9`. To restore the legacy behavior, you can set `spark.speculation.multiplier=1.5` and `spark.speculation.quantile=0.75`.
 
 ## Upgrading from Core 3.4 to 3.5