Marius Müller-Westernhagen (born 6 December 1948) is a German musician and actor. He has been a feature in German rock music since the mid-1970s. Müller-Westernhagen is known for his energetic public concerts, and his fans know his anthem-like songs by heart. Though written a few years earlier, his song "Freiheit" ("Freedom") is widely considered as an anthem of the German Reunification.

While keeping away from the merely fashionable, Müller-Westernhagen has nevertheless managed to reinvent himself every few years, and is popular with multiple generations of Germans. As a result of his singing which almost exclusively in German language in a country where pop and rock are primarily performed in English, Westernhagen originally seemed destined for obscurity, but has managed to use this to his advantage, defining himself as a durable alternative to the perceivably manufactured English-language hits of the US and UK.

Müller-Westernhagen has also acted in films and in radio.