diff --git a/features/access.feature b/features/access.feature
index 9960f38..1aaddb8 100644
--- a/features/access.feature
+++ b/features/access.feature
@@ -2,19 +2,28 @@ Feature: Session access
   Scenario: Check data does not exist
     When data does not exist
     Then property check returns false
+    And array access check returns false
   Scenario: Check data exist
     When data exists
     Then property check returns true
+    And array access check returns true
   Scenario: Read data that exists
     When data exists
     Then property read returns data
+    And array access read returns data
   Scenario: Read data that does not exist
     When data does not exist
     Then property read triggers error
     And property read returns null
+    And array access read triggers error
+    And array access read returns null
   Scenario: Null coalesce when data does not exist
     When data does not exist
     Then property read with null coalesce returns null
-  Scenario: Write data
+    And array access read with null coalesce returns null
+  Scenario: Write property data
     When data does not exist
     Then property write succeeds
+  Scenario: Write array access data
+    When data does not exist
+    Then array access write succeeds
diff --git a/src/Session.php b/src/Session.php
index 02db40e..0077a42 100644
--- a/src/Session.php
+++ b/src/Session.php
@@ -5,9 +5,10 @@
 namespace Compwright\PhpSession;
 
 use Countable;
+use ArrayAccess;
 use RuntimeException;
 
-class Session implements Countable
+class Session implements ArrayAccess, Countable
 {
     protected string $name;
 
@@ -94,6 +95,48 @@ public function __unset(string $name): void
         unset($this->contents[$name]);
     }
 
+    public function offsetSet($name, $value): void
+    {
+        if (!$this->isInitialized()) {
+            throw new RuntimeException('Session not initialized');
+        }
+
+        if (!$this->writeable) {
+            throw new RuntimeException('Cannot alter session after it is closed');
+        }
+
+        $this->modified = true;
+        $this->contents[$name] = $value;
+    }
+
+    public function offsetExists($name): bool
+    {
+        if (!$this->isInitialized()) {
+            throw new RuntimeException('Session not initialized');
+        }
+
+        return isset($this->contents[$name]);
+    }
+
+    public function offsetUnset($name): void
+    {
+        if (!$this->isInitialized()) {
+            throw new RuntimeException('Session not initialized');
+        }
+
+        if (!$this->writeable) {
+            throw new RuntimeException('Cannot alter session after it is closed');
+        }
+
+        $this->modified = true;
+        unset($this->contents[$name]);
+    }
+
+    public function offsetGet($name): mixed
+    {
+        return $this->contents[$name];
+    }
+
     /**
      * @param ?array<string, mixed> $contents
      */
diff --git a/tests/behavior/AccessContext.php b/tests/behavior/AccessContext.php
index fd91a08..d3c4bc5 100644
--- a/tests/behavior/AccessContext.php
+++ b/tests/behavior/AccessContext.php
@@ -101,4 +101,72 @@ public function propertyWriteSucceeds(): void
         Assert::assertCount(1, $this->session);
         Assert::assertTrue(isset($this->session->bar));
     }
+
+    /**
+     * @Then array access check returns true
+     */
+    public function arrayAccessCheckReturnsTrue(): void
+    {
+        Assert::assertTrue(isset($this->session['foo']));
+    }
+
+    /**
+     * @Then array access check returns false
+     */
+    public function arrayAccessCheckReturnsFalse(): void
+    {
+        Assert::assertFalse(isset($this->session['foo']));
+    }
+
+    /**
+     * @Then array access read returns data
+     */
+    public function arrayAccessReadReturnsData(): void
+    {
+        Assert::assertEquals('bar', $this->session['foo']);
+    }
+
+    /**
+     * @Then array access read triggers error
+     */
+    public function arrayAccessReadTriggersNoticeError(): void
+    {
+        try {
+            $errorThrown = false;
+            $bar = $this->session['bar'];
+            // @phpstan-ignore-next-line
+        } catch (Throwable $e) {
+            $errorThrown = true;
+        } finally {
+            Assert::assertTrue($errorThrown);
+        }
+    }
+
+    /**
+     * @Then array access read returns null
+     */
+    public function arrayAccessReadReturnsNull(): void
+    {
+        $bar = @$this->session['foo'];
+        Assert::assertSame(null, $bar);
+    }
+
+    /**
+     * @Then array access read with null coalesce returns null
+     */
+    public function arrayAccessReadWithNullCoalesceReturnsNull(): void
+    {
+        $bar = $this->session['foo'] ?? null;
+        Assert::assertSame(null, $bar);
+    }
+
+    /**
+     * @Then array access write succeeds
+     */
+    public function arrayAccessWriteSucceeds(): void
+    {
+        $this->session['bar'] = 'baz';
+        Assert::assertCount(1, $this->session);
+        Assert::assertTrue(isset($this->session['bar']));
+    }
 }