diff --git a/README.md b/README.md
index 6eabaa1..c07bbd7 100644
--- a/README.md
+++ b/README.md
@@ -119,6 +119,56 @@ try {
 }
 ```
 
+### Using Two-Legged Authentication (Oauth2 Client Credentials) Instead
+The above method uses authorization code flow for Oauth2. Client Credentials is the preferred method of
+authentication when the use-case is application to application, where any actions
+are triggered by the application itself and not a user taking an action (e.g. cleanup during cron).
+
+```php
+<?php
+
+// Bootup the Composer autoloader
+include __DIR__ . '/vendor/autoload.php';
+
+use Mautic\Auth\ApiAuth;
+
+session_start();
+
+$publicKey = '';
+$secretKey = '';
+$callback  = '';
+
+// ApiAuth->newAuth() will accept an array of Auth settings
+$settings = [
+    'AuthMethod'   => 'TwoLeggedOAuth2',
+    'clientKey'    => '',
+    'clientSecret' => '',
+    'baseUrl'      => '',
+];
+
+/*
+// If you already have the access token, et al, pass them in as well to prevent the need for reauthorization
+$settings['accessToken']        = $accessToken;
+$settings['accessTokenExpires'] = $accessTokenExpires; //UNIX timestamp
+*/
+
+// Initiate the auth object
+$initAuth = new ApiAuth();
+$auth     = $initAuth->newAuth($settings, $settings['AuthMethod']);
+
+if (!$auth->isAuthorized()) {
+    $auth->requestAccessToken();
+    // $accessTokenData will have the following keys:
+    // access_token, expires, token_type
+    $accessTokenData = $auth->getAccessTokenData();
+
+    //store access token data however you want
+}
+
+// Nothing else to do ... It's ready to use.
+// Just pass the auth object to the API context you are creating.
+```
+
 ### Using Basic Authentication Instead
 Instead of messing around with OAuth, you may simply elect to use BasicAuth instead.
 
diff --git a/lib/Auth/TwoLeggedOAuth2.php b/lib/Auth/TwoLeggedOAuth2.php
new file mode 100755
index 0000000..8b1a398
--- /dev/null
+++ b/lib/Auth/TwoLeggedOAuth2.php
@@ -0,0 +1,241 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Mautic\Auth;
+
+use Mautic\Exception\IncorrectParametersReturnedException;
+use Mautic\Exception\RequiredParameterMissingException;
+
+/**
+ * @internal OAuth Client modified from https://code.google.com/p/simple-php-oauth/.
+ */
+class TwoLeggedOAuth2 extends AbstractAuth
+{
+    /**
+     * Access token URL.
+     */
+    protected string $_access_token_url;
+
+    /**
+     * Access token returned by OAuth server.
+     */
+    protected ?string $_access_token;
+
+    /**
+     * Consumer or client key.
+     */
+    protected string $_client_id;
+
+    /**
+     * Consumer or client secret.
+     */
+    protected string $_client_secret;
+
+    /**
+     * Unix timestamp for when token expires.
+     */
+    protected ?int $_expires;
+
+    /**
+     * OAuth2 token type.
+     */
+    protected ?string $_token_type = 'bearer';
+
+    /**
+     * Set to true if the access token was updated.
+     */
+    protected bool $_access_token_updated = false;
+
+    /**
+     * @param string|null $baseUrl URL of the Mautic instance
+     */
+    public function setup(
+        ?string $baseUrl = null,
+        ?string $clientKey = null,
+        ?string $clientSecret = null,
+        ?string $accessToken = null,
+        ?int $accessTokenExpires = null,
+    ): void {
+        if (empty($clientKey) || empty($clientSecret)) {
+            // Throw exception if the required parameters were not found
+            $this->log('parameters did not include clientkey and/or clientSecret');
+            throw new RequiredParameterMissingException('One or more required parameters was not supplied. Both clientKey and clientSecret required!');
+        }
+
+        if (empty($baseUrl)) {
+            // Throw exception if the required parameters were not found
+            $this->log('parameters did not include baseUrl');
+            throw new RequiredParameterMissingException('One or more required parameters was not supplied. baseUrl required!');
+        }
+
+        $this->_client_id        = $clientKey;
+        $this->_client_secret    = $clientSecret;
+        $this->_access_token     = $accessToken;
+        $this->_access_token_url = $baseUrl.'/oauth/v2/token';
+
+        if (!empty($accessToken)) {
+            $this->setAccessTokenDetails([
+                'access_token' => $accessToken,
+                'expires'      => $accessTokenExpires,
+            ]);
+        }
+    }
+
+    /**
+     * Check to see if the access token was updated.
+     *
+     * @return bool
+     */
+    public function accessTokenUpdated()
+    {
+        return $this->_access_token_updated;
+    }
+
+    /**
+     * Returns access token data.
+     */
+    public function getAccessTokenData(): array
+    {
+        return [
+            'access_token' => $this->_access_token,
+            'expires'      => $this->_expires,
+            'token_type'   => $this->_token_type,
+        ];
+    }
+
+    public function isAuthorized(): bool
+    {
+        $this->log('isAuthorized()');
+
+        return $this->validateAccessToken();
+    }
+
+    /**
+     * Set an existing/already retrieved access token.
+     *
+     * @return $this
+     */
+    public function setAccessTokenDetails(array $accessTokenDetails): static
+    {
+        $this->_access_token = $accessTokenDetails['access_token'] ?? null;
+        $this->_expires      = isset($accessTokenDetails['expires']) ? (int) $accessTokenDetails['expires'] : null;
+
+        return $this;
+    }
+
+    /**
+     * Validate existing access token.
+     */
+    public function validateAccessToken(): bool
+    {
+        $this->log('validateAccessToken()');
+
+        // Check to see if token in session has expired (or will in a few seconds)
+        if (!empty($this->_access_token) && !empty($this->_expires) && $this->_expires < (time() + 10)) {
+            $this->log('access token expired');
+
+            return false;
+        }
+
+        // Check for existing access token
+        if (!empty($this->_access_token)) {
+            $this->log('has valid access token');
+
+            return true;
+        }
+
+        // If there is no existing access token, it can't be valid
+        return false;
+    }
+
+    /**
+     * @param bool  $isPost
+     * @param array $parameters
+     */
+    protected function getQueryParameters($isPost, $parameters): array
+    {
+        $query = parent::getQueryParameters($isPost, $parameters);
+
+        if (isset($parameters['file'])) {
+            // Mautic's OAuth2 server does not recognize multipart forms so we have to append the access token as part of the URL
+            $query['access_token'] = $parameters['access_token'];
+        }
+
+        return $query;
+    }
+
+    /**
+     * @param string $url
+     * @param array  $method
+     */
+    protected function prepareRequest($url, array $headers, array $parameters, $method, array $settings): array
+    {
+        if ($this->isAuthorized()) {
+            $headers = array_merge($headers, ['Authorization: Bearer '.$this->_access_token]);
+        }
+
+        return [$headers, $parameters];
+    }
+
+    /**
+     * Request access token.
+     *
+     * @throws IncorrectParametersReturnedException|\Mautic\Exception\UnexpectedResponseFormatException
+     */
+    public function requestAccessToken(): bool
+    {
+        $this->log('requestAccessToken()');
+
+        $parameters = [
+            'client_id'     => $this->_client_id,
+            'client_secret' => $this->_client_secret,
+            'grant_type'    => 'client_credentials',
+        ];
+
+        // Make the request
+        $params = $this->makeRequest($this->_access_token_url, $parameters, 'POST');
+
+        // Add the token to session
+        if (is_array($params)) {
+            if (isset($params['access_token']) && isset($params['expires_in'])) {
+                $this->log('access token set as '.$params['access_token']);
+
+                $this->_access_token         = $params['access_token'];
+                $this->_expires              = time() + (int) $params['expires_in'];
+                $this->_token_type           = (isset($params['token_type'])) ? $params['token_type'] : null;
+                $this->_access_token_updated = true;
+
+                if ($this->_debug) {
+                    $_SESSION['oauth']['debug']['tokens']['access_token'] = $params['access_token'];
+                    $_SESSION['oauth']['debug']['tokens']['expires_in']   = $params['expires_in'];
+                    $_SESSION['oauth']['debug']['tokens']['token_type']   = $params['token_type'];
+                }
+
+                return true;
+            }
+        }
+
+        $this->log('response did not have an access token');
+
+        if ($this->_debug) {
+            $_SESSION['oauth']['debug']['response'] = $params;
+        }
+
+        if (is_array($params)) {
+            if (isset($params['errors'])) {
+                $errors = [];
+                foreach ($params['errors'] as $error) {
+                    $errors[] = $error['message'];
+                }
+                $response = implode('; ', $errors);
+            } else {
+                $response = print_r($params, true);
+            }
+        } else {
+            $response = $params;
+        }
+
+        throw new IncorrectParametersReturnedException('Incorrect access token parameters returned: '.$response);
+    }
+}