diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65ea279b4..46ae50a2c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -47,6 +47,7 @@ The major version bump is due to upping the required PHP version from `8.5` to `
 * Added the following methods to the `ImageInterface` interface:
 	- `ImageInterface::toBase64()`
 	- `ImageInterface::toDataUri()`
+* Added dotenv loader.
 
 #### Changes
 
diff --git a/src/mako/env/DotenvLoader.php b/src/mako/env/DotenvLoader.php
new file mode 100644
index 000000000..3d2555c53
--- /dev/null
+++ b/src/mako/env/DotenvLoader.php
@@ -0,0 +1,268 @@
+<?php
+
+/**
+ * @copyright Frederic G. Østby
+ * @license   http://www.makoframework.com/license
+ */
+
+namespace mako\env;
+
+use mako\env\exceptions\EnvException;
+
+use function array_key_exists;
+use function ctype_space;
+use function file;
+use function getenv;
+use function mako\env;
+use function preg_match;
+use function preg_replace_callback;
+use function putenv;
+use function rtrim;
+use function sprintf;
+use function str_contains;
+use function str_replace;
+use function str_starts_with;
+use function strlen;
+use function strpos;
+use function substr;
+use function trim;
+
+/**
+ * Dotenv loader.
+ */
+final class DotenvLoader
+{
+	/**
+	 * Constructor.
+	 */
+	public function __construct(
+		private bool $overrideExisting = false,
+		private bool $interpolateVariables = false,
+		private bool $usePutEnv = false
+	) {
+	}
+
+	/**
+	 * Strip inline comment from value.
+	 */
+	private function stripInlineComment(string $value): string
+	{
+		$quote = ($value[0] === '"' || $value[0] === "'") ? $value[0] : null;
+		$escaped = false;
+
+		$length = strlen($value);
+
+		for ($i = 0; $i < $length; $i++) {
+			$char = $value[$i];
+
+			if ($quote !== null) {
+				if ($i === 0) {
+					continue;
+				}
+
+				if ($quote === '"' && $char === '\\' && !$escaped) {
+					$escaped = true;
+					continue;
+				}
+
+				if ($char === $quote && !$escaped) {
+					$quote = null;
+					continue;
+				}
+
+				$escaped = false;
+				continue;
+			}
+
+			if ($char === '#' && $i > 0 && ctype_space($value[$i - 1])) {
+				return rtrim(substr($value, 0, $i));
+			}
+		}
+
+		return $value;
+	}
+
+	/**
+	 * Interpolate variables in value.
+	 */
+	private function interpolateVariables(string $value, string $filePath, int $lineNumber): string
+	{
+		return preg_replace_callback(
+			'/(\\\\*)\$\{([A-Z_][A-Z0-9_]*)\}/i',
+			static function (array $matches) use ($filePath, $lineNumber): string {
+				$slashes = $matches[1];
+				$key = $matches[2];
+
+				// Odd number of backslashes escapes the variable
+
+				if ((strlen($slashes) % 2) === 1) {
+					return substr($slashes, 1) . "\${{$key}}";
+				}
+
+				// Even number of backslashes, we'll expand the variable
+
+				return $slashes . (
+					env($key)
+					?? throw new EnvException(sprintf(
+						'Undefined environment variable [ $%s ] in [ %s ] on line [ %s ].',
+						$key,
+						$filePath,
+						$lineNumber
+					))
+				);
+			},
+			$value
+		) ?? $value;
+	}
+
+	/**
+	 * Unescape values.
+	 */
+	private function unescape(string $value): string
+	{
+		return str_replace(
+			['\\n', '\\r', '\\t', '\\"', '\\\\'],
+			["\n", "\r", "\t", '"', '\\'],
+			$value
+		);
+	}
+
+	/**
+	 * Parse value.
+	 */
+	private function parseValue(string $value, string $filePath, int $lineNumber): string
+	{
+		// Remove inline comments
+
+		if (strpos($value, '#') !== false) {
+			$value = $this->stripInlineComment($value);
+		}
+
+		if ($value === '') {
+			return '';
+		}
+
+		// Get first and last character
+
+		$first = $value[0];
+		$last = $value[strlen($value) - 1];
+
+		// Quoted value
+
+		if ($first === '"' || $first === "'") {
+			if ($last !== $first) {
+				throw new EnvException(sprintf(
+					'Unterminated quoted value in [ %s ] on line [ %s ].',
+					$filePath,
+					$lineNumber
+				));
+			}
+
+			$value = substr($value, 1, -1);
+
+			if ($first === '"') {
+				if ($this->interpolateVariables && strpos($value, '${') !== false) {
+					$value = $this->interpolateVariables($value, $filePath, $lineNumber);
+				}
+
+				$value = $this->unescape($value);
+			}
+
+			return $value;
+		}
+
+		// Unquoted value so we'll just trim it and return
+
+		return trim($value);
+	}
+
+	/**
+	 * Loads the file into environment variables.
+	 */
+	public function load(string $filePath, string $keyPrefix = ''): void
+	{
+		$lines = file($filePath, FILE_IGNORE_NEW_LINES);
+
+		if ($lines === false) {
+			throw new EnvException(sprintf('Failed to read env file [ %s ].', $filePath));
+		}
+
+		foreach ($lines as $key => $line) {
+			$lineNumber = $key + 1;
+
+			// Check for NUL byte
+
+			if (str_contains($line, "\0")) {
+				throw new EnvException(sprintf(
+					'NUL byte detected in [ %s ] on line [ %s ].',
+					$filePath,
+					$lineNumber
+				));
+			}
+
+			// Strip UTF-8 BOM from first line
+
+			if ($lineNumber === 1 && str_starts_with($line, "\xEF\xBB\xBF")) {
+				$line = substr($line, 3);
+			}
+
+			$line = trim($line);
+
+			// Skip empty lines and lines that are comments
+
+			if ($line === '' || str_starts_with($line, '#')) {
+				continue;
+			}
+
+			// Strip "export" line prefix
+
+			if (str_starts_with($line, 'export ')) {
+				$line = trim(substr($line, 7));
+			}
+
+			// Split key and value
+
+			$equalPosition = strpos($line, '=');
+
+			if ($equalPosition === false) {
+				throw new EnvException(sprintf(
+					'Invalid env declaration in [ %s ] on line [ %s ].',
+					$filePath,
+					$lineNumber
+				));
+			}
+
+			$key = trim(substr($line, 0, $equalPosition));
+			$value = trim(substr($line, $equalPosition + 1));
+
+			if ($key === '' || !preg_match('/^(?:[A-Z][A-Z0-9_]*|_[A-Z0-9_]+)$/i', $key)) {
+				throw new EnvException(sprintf(
+					'Invalid key [ %s ] in [ %s ] on line [ %s ].',
+					($key ?: 'empty'),
+					$filePath,
+					$lineNumber
+				));
+			}
+
+			$key = "{$keyPrefix}{$key}";
+
+			// Should we skip overriding existing variables?
+
+			if ($this->overrideExisting === false && (array_key_exists($key, $_ENV) || getenv($key) !== false)) {
+				continue;
+			}
+
+			// Parse value and put it into environment
+
+			if ($value !== '') {
+				$value = $this->parseValue($value, $filePath, $lineNumber);
+			}
+
+			if ($this->usePutEnv) {
+				putenv("{$key}={$value}");
+			}
+
+			$_ENV[$key] = $value;
+		}
+	}
+}
diff --git a/src/mako/env/exceptions/EnvException.php b/src/mako/env/exceptions/EnvException.php
new file mode 100644
index 000000000..310f854bd
--- /dev/null
+++ b/src/mako/env/exceptions/EnvException.php
@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @copyright Frederic G. Østby
+ * @license   http://www.makoframework.com/license
+ */
+
+namespace mako\env\exceptions;
+
+use RuntimeException;
+
+/**
+ * Env exception.
+ */
+class EnvException extends RuntimeException
+{
+
+}
diff --git a/src/mako/functions.php b/src/mako/functions.php
index c14f0c3f3..889eb47d4 100644
--- a/src/mako/functions.php
+++ b/src/mako/functions.php
@@ -32,7 +32,7 @@ function f(string $_name, mixed ...$_arguments): string
 	 */
 	function env(string $variableName, mixed $default = null, bool $localOnly = false, ?Type $as = null): mixed
 	{
-		$value = $_ENV[$variableName] ?? (getenv($variableName, $localOnly) ?: null);
+		$value = $_ENV[$variableName] ?? (($env = getenv($variableName, $localOnly)) !== false ? $env : null);
 
 		return match ($as) {
 			null => $value,
diff --git a/tests/unit/env/DotenvLoaderTest.php b/tests/unit/env/DotenvLoaderTest.php
new file mode 100644
index 000000000..06a8e812f
--- /dev/null
+++ b/tests/unit/env/DotenvLoaderTest.php
@@ -0,0 +1,194 @@
+<?php
+
+/**
+ * @copyright Frederic G. Østby
+ * @license   http://www.makoframework.com/license
+ */
+
+namespace mako\tests\unit\env;
+
+use mako\env\DotenvLoader;
+use mako\env\exceptions\EnvException;
+use mako\tests\TestCase;
+use PHPUnit\Framework\Attributes\Group;
+
+#[Group('unit')]
+class DotenvLoaderTest extends TestCase
+{
+	/**
+	 *
+	 */
+	public function testLoadBasic(): void
+	{
+		(new DotenvLoader)
+		->load(__DIR__ . '/fixtures/basic.env', 'MAKO_TEST_');
+
+		$this->assertSame('value#1', $_ENV['MAKO_TEST_KEY1']);
+		$this->assertSame('value#2', $_ENV['MAKO_TEST_KEY2']);
+		$this->assertSame('value#3', $_ENV['MAKO_TEST_KEY3']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY4']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY5']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY6']);
+		$this->assertSame('value#7', $_ENV['MAKO_TEST_KEY7']);
+		$this->assertSame('value#8', $_ENV['MAKO_TEST_KEY8']);
+		$this->assertSame('value#9', $_ENV['MAKO_TEST_KEY9']);
+		$this->assertSame('value#10', $_ENV['MAKO_TEST_KEY10']);
+		$this->assertSame('value#11', $_ENV['MAKO_TEST_KEY11']);
+		$this->assertSame('value#12', $_ENV['MAKO_TEST_KEY12']);
+		$this->assertSame('value#13', $_ENV['MAKO_TEST_KEY13']);
+		$this->assertSame('value#14', $_ENV['MAKO_TEST_KEY14']);
+		$this->assertSame('value#15', $_ENV['MAKO_TEST_KEY15']);
+		$this->assertSame('foo\nbar', $_ENV['MAKO_TEST_KEY16']);
+		$this->assertSame('foo\nbar', $_ENV['MAKO_TEST_KEY17']);
+		$this->assertSame("foo\nbar", $_ENV['MAKO_TEST_KEY18']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY19']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY20']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY21']);
+		$this->assertSame('var:\\\\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY22']);
+		$this->assertSame('var:\\\\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY23']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY24']);
+		$this->assertSame('value#25', $_ENV['MAKO_TEST_KEY25']);
+		$this->assertSame('value#26', $_ENV['MAKO_TEST_KEY26']);
+		$this->assertSame('value#27', $_ENV['MAKO_TEST_KEY27']);
+
+		foreach (range(1, 27) as $num) {
+			unset($_ENV["MAKO_TEST_KEY{$num}"]);
+		}
+	}
+
+	/**
+	 *
+	 */
+	public function testLoadBasicWithInterpolatedVariables(): void
+	{
+		(new DotenvLoader(interpolateVariables: true))
+		->load(__DIR__ . '/fixtures/basic.env', 'MAKO_TEST_');
+
+		$this->assertSame('value#1', $_ENV['MAKO_TEST_KEY1']);
+		$this->assertSame('value#2', $_ENV['MAKO_TEST_KEY2']);
+		$this->assertSame('value#3', $_ENV['MAKO_TEST_KEY3']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY4']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY5']);
+		$this->assertSame('var:value#1', $_ENV['MAKO_TEST_KEY6']);
+		$this->assertSame('value#7', $_ENV['MAKO_TEST_KEY7']);
+		$this->assertSame('value#8', $_ENV['MAKO_TEST_KEY8']);
+		$this->assertSame('value#9', $_ENV['MAKO_TEST_KEY9']);
+		$this->assertSame('value#10', $_ENV['MAKO_TEST_KEY10']);
+		$this->assertSame('value#11', $_ENV['MAKO_TEST_KEY11']);
+		$this->assertSame('value#12', $_ENV['MAKO_TEST_KEY12']);
+		$this->assertSame('value#13', $_ENV['MAKO_TEST_KEY13']);
+		$this->assertSame('value#14', $_ENV['MAKO_TEST_KEY14']);
+		$this->assertSame('value#15', $_ENV['MAKO_TEST_KEY15']);
+		$this->assertSame('foo\nbar', $_ENV['MAKO_TEST_KEY16']);
+		$this->assertSame('foo\nbar', $_ENV['MAKO_TEST_KEY17']);
+		$this->assertSame("foo\nbar", $_ENV['MAKO_TEST_KEY18']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY19']);
+		$this->assertSame('var:\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY20']);
+		$this->assertSame('var:${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY21']);
+		$this->assertSame('var:\\\\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY22']);
+		$this->assertSame('var:\\\\${MAKO_TEST_KEY1}', $_ENV['MAKO_TEST_KEY23']);
+		$this->assertSame('var:\value#1', $_ENV['MAKO_TEST_KEY24']);
+		$this->assertSame('value#25', $_ENV['MAKO_TEST_KEY25']);
+		$this->assertSame('value#26', $_ENV['MAKO_TEST_KEY26']);
+		$this->assertSame('value#27', $_ENV['MAKO_TEST_KEY27']);
+
+		foreach (range(1, 27) as $num) {
+			unset($_ENV["MAKO_TEST_KEY{$num}"]);
+		}
+	}
+
+	/**
+	 *
+	 */
+	public function testNoOverride(): void
+	{
+		(new DotenvLoader)
+		->load(__DIR__ . '/fixtures/override.env', 'MAKO_TEST_');
+
+		$this->assertSame('foo', $_ENV['MAKO_TEST_KEY1']);
+
+		unset($_ENV['MAKO_TEST_KEY1']);
+	}
+
+	/**
+	 *
+	 */
+	public function testWithOverride(): void
+	{
+		(new DotenvLoader(overrideExisting: true))
+		->load(__DIR__ . '/fixtures/override.env', 'MAKO_TEST_');
+
+		$this->assertSame('bar', $_ENV['MAKO_TEST_KEY1']);
+
+		unset($_ENV['MAKO_TEST_KEY1']);
+	}
+
+	/**
+	 *
+	 */
+	public function testInvalidDeclaration(): void
+	{
+		$file = __DIR__ . '/fixtures/invalid-declaration.env';
+
+		$this->expectException(EnvException::class);
+		$this->expectExceptionMessageIs('Invalid env declaration in [ ' . $file . ' ] on line [ 1 ].');
+
+		(new DotenvLoader)->load($file, 'MAKO_TEST_');
+	}
+
+	/**
+	 *
+	 */
+	public function testInvalidKey(): void
+	{
+		$file = __DIR__ . '/fixtures/invalid-key.env';
+
+		$this->expectException(EnvException::class);
+		$this->expectExceptionMessageIs('Invalid key [ $KEY1 ] in [ ' . $file . ' ] on line [ 1 ].');
+
+		(new DotenvLoader)
+		->load($file, 'MAKO_TEST_');
+	}
+
+	/**
+	 *
+	 */
+	public function testUnterminatedDoubleQuote(): void
+	{
+		$file = __DIR__ . '/fixtures/unterminated-double-quote.env';
+
+		$this->expectException(EnvException::class);
+		$this->expectExceptionMessageIs('Unterminated quoted value in [ ' . $file . ' ] on line [ 1 ].');
+
+		(new DotenvLoader)
+		->load($file, 'MAKO_TEST_');
+	}
+
+	/**
+	 *
+	 */
+	public function testUnterminatedSingleQuote(): void
+	{
+		$file = __DIR__ . '/fixtures/unterminated-single-quote.env';
+
+		$this->expectException(EnvException::class);
+		$this->expectExceptionMessageIs('Unterminated quoted value in [ ' . $file . ' ] on line [ 1 ].');
+
+		(new DotenvLoader)
+		->load($file, 'MAKO_TEST_');
+	}
+
+	/**
+	 *
+	 */
+	public function testUndefinedVariable(): void
+	{
+		$file = __DIR__ . '/fixtures/undefined-variable.env';
+
+		$this->expectException(EnvException::class);
+		$this->expectExceptionMessageIs('Undefined environment variable [ $MAKO_TEST_FOO_BAR_BAZ ] in [ ' . $file . ' ] on line [ 1 ].');
+
+		(new DotenvLoader(interpolateVariables: true))
+		->load($file, 'MAKO_TEST_');
+	}
+}
diff --git a/tests/unit/env/fixtures/basic.env b/tests/unit/env/fixtures/basic.env
new file mode 100644
index 000000000..9ddf86ad2
--- /dev/null
+++ b/tests/unit/env/fixtures/basic.env
@@ -0,0 +1,35 @@
+KEY1=value#1 #comment
+KEY2='value#2' #comment
+KEY3="value#3" #comment
+
+KEY4=var:${MAKO_TEST_KEY1}
+KEY5='var:${MAKO_TEST_KEY1}'
+KEY6="var:${MAKO_TEST_KEY1}"
+
+KEY7= value#7
+KEY8= 'value#8'
+KEY9= "value#9"
+
+KEY10 =value#10
+KEY11 ='value#11'
+KEY12 ="value#12"
+
+KEY13 = value#13
+KEY14 = 'value#14'
+KEY15 = "value#15"
+
+KEY16 = foo\nbar
+KEY17 = 'foo\nbar'
+KEY18 = "foo\nbar"
+
+KEY19=var:\${MAKO_TEST_KEY1}
+KEY20='var:\${MAKO_TEST_KEY1}'
+KEY21="var:\${MAKO_TEST_KEY1}"
+
+KEY22=var:\\${MAKO_TEST_KEY1}
+KEY23='var:\\${MAKO_TEST_KEY1}'
+KEY24="var:\\${MAKO_TEST_KEY1}"
+
+export KEY25= value#25
+export  KEY26= 'value#26'
+export   KEY27= "value#27"
diff --git a/tests/unit/env/fixtures/invalid-declaration.env b/tests/unit/env/fixtures/invalid-declaration.env
new file mode 100644
index 000000000..7aa1ee343
--- /dev/null
+++ b/tests/unit/env/fixtures/invalid-declaration.env
@@ -0,0 +1 @@
+KEY1
diff --git a/tests/unit/env/fixtures/invalid-key.env b/tests/unit/env/fixtures/invalid-key.env
new file mode 100644
index 000000000..65eb09bfa
--- /dev/null
+++ b/tests/unit/env/fixtures/invalid-key.env
@@ -0,0 +1 @@
+$KEY1=foo
diff --git a/tests/unit/env/fixtures/override.env b/tests/unit/env/fixtures/override.env
new file mode 100644
index 000000000..790b34cad
--- /dev/null
+++ b/tests/unit/env/fixtures/override.env
@@ -0,0 +1,2 @@
+KEY1=foo
+KEY1=bar
diff --git a/tests/unit/env/fixtures/undefined-variable.env b/tests/unit/env/fixtures/undefined-variable.env
new file mode 100644
index 000000000..eaf207156
--- /dev/null
+++ b/tests/unit/env/fixtures/undefined-variable.env
@@ -0,0 +1 @@
+KEY1="${MAKO_TEST_FOO_BAR_BAZ}"
diff --git a/tests/unit/env/fixtures/unterminated-double-quote.env b/tests/unit/env/fixtures/unterminated-double-quote.env
new file mode 100644
index 000000000..701130fd2
--- /dev/null
+++ b/tests/unit/env/fixtures/unterminated-double-quote.env
@@ -0,0 +1 @@
+KEY1="value
diff --git a/tests/unit/env/fixtures/unterminated-single-quote.env b/tests/unit/env/fixtures/unterminated-single-quote.env
new file mode 100644
index 000000000..88c5d7fdf
--- /dev/null
+++ b/tests/unit/env/fixtures/unterminated-single-quote.env
@@ -0,0 +1 @@
+KEY1='value