diff --git a/src/Monolog/Logger.php b/src/Monolog/Logger.php
index 099185205..1ab75b9e0 100644
--- a/src/Monolog/Logger.php
+++ b/src/Monolog/Logger.php
@@ -111,6 +111,22 @@ class Logger implements LoggerInterface, ResettableInterface
         self::EMERGENCY => 'EMERGENCY',
     ];
 
+    /**
+     * Mapping between levels numbers defined in RFC 5424 and Monolog ones
+     *
+     * @phpstan-var array<int, Level> $rfc_5424_levels
+     */
+    private const RFC_5424_LEVELS = [
+        7 => self::DEBUG,
+        6 => self::INFO,
+        5 => self::NOTICE,
+        4 => self::WARNING,
+        3 => self::ERROR,
+        2 => self::CRITICAL,
+        1 => self::ALERT,
+        0 => self::EMERGENCY,
+    ];
+
     /**
      * @var string
      */
@@ -301,7 +317,7 @@ public function useLoggingLoopDetection(bool $detectCycles): self
     /**
      * Adds a log record.
      *
-     * @param  int               $level    The logging level
+     * @param  int               $level    The logging level (a Monolog or RFC 5424 level)
      * @param  string            $message  The log message
      * @param  mixed[]           $context  The log context
      * @param  DateTimeImmutable $datetime Optional log date to log into the past or future
@@ -311,6 +327,10 @@ public function useLoggingLoopDetection(bool $detectCycles): self
      */
     public function addRecord(int $level, string $message, array $context = [], DateTimeImmutable $datetime = null): bool
     {
+        if (isset(self::RFC_5424_LEVELS[$level])) {
+            $level = self::RFC_5424_LEVELS[$level];
+        }
+
         if ($this->detectCycles) {
             $this->logDepth += 1;
         }
@@ -520,7 +540,7 @@ public function getExceptionHandler(): ?callable
      *
      * This method allows for compatibility with common interfaces.
      *
-     * @param mixed             $level   The log level
+     * @param mixed             $level   The log level (a Monolog, PSR-3 or RFC 5424 level)
      * @param string|Stringable $message The log message
      * @param mixed[]           $context The log context
      *
@@ -532,6 +552,10 @@ public function log($level, $message, array $context = []): void
             throw new \InvalidArgumentException('$level is expected to be a string or int');
         }
 
+        if (isset(self::RFC_5424_LEVELS[$level])) {
+            $level = self::RFC_5424_LEVELS[$level];
+        }
+
         $level = static::toMonologLevel($level);
 
         $this->addRecord($level, (string) $message, $context);
diff --git a/tests/Monolog/LoggerTest.php b/tests/Monolog/LoggerTest.php
index 0b07a7cf1..fd99df206 100644
--- a/tests/Monolog/LoggerTest.php
+++ b/tests/Monolog/LoggerTest.php
@@ -62,6 +62,37 @@ public function testConvertPSR3ToMonologLevel()
         $this->assertEquals(Logger::toMonologLevel('emergency'), 600);
     }
 
+    /**
+     * @covers Monolog\Logger::addRecord
+     * @covers Monolog\Logger::log
+     */
+    public function testConvertRFC5424ToMonologLevelInAddRecordAndLog()
+    {
+        $logger = new Logger('test');
+        $handler = new TestHandler;
+        $logger->pushHandler($handler);
+
+        foreach ([
+            7 => 100,
+            6 => 200,
+            5 => 250,
+            4 => 300,
+            3 => 400,
+            2 => 500,
+            1 => 550,
+            0 => 600,
+        ] as $rfc5424Level => $monologLevel) {
+            $handler->reset();
+            $logger->addRecord($rfc5424Level, 'test');
+            $logger->log($rfc5424Level, 'test');
+            $records = $handler->getRecords();
+
+            self::assertCount(2, $records);
+            self::assertSame($monologLevel, $records[0]['level']);
+            self::assertSame($monologLevel, $records[1]['level']);
+        }
+    }
+
     /**
      * @covers Monolog\Logger::getLevelName
      */