Marian Kociniak (11 January 1936, Warsaw - 17 March 2016, Warsaw ) was a Polish film and theatre actor, most notable for appearing in the 1970 film How I Unleashed World War II.

Kociniak graduated from The Aleksander Zelwerowicz National Academy of Dramatic Art in Warsaw in 1959 from the teachings of Ludwik Sempoliński. Since 1959, almost without interruption, he acts in the Ateneum Theatre. He appeared on televised Theatre, reenacting many novels from the time. He also appeared in Kabaret Starszych Panów. His screen debut came in the 1959 film Mr. Professor. He appeared in over 30 films since then. He also collaborated with radio appearing in the magazine 60 minut na godzinę, where he paired with Andrzej Zaorski on Polskie Radio Program III.

The popularity of the actor influenced creations of Frank Dolas in the famous Polish comedy How I Unleashed World War II and as a burgrave in the show Janosik, directed by Jerzy Passendorfer.

In 2003, during the VIII Festival of Stars in Międzyzdroje artist he performed on the Promenade of Stars.

From the beginning of his career he does not agree to interviews. The exception is the interview for the BBC to mark the 50th anniversary of his artistic work.

Since 2010, he has been working with the Wola theatre.

He was an honorary member of the support committee for Bronislaw Komorowski ahead accelerated presidential elections in 2010 and before the presidential elections in Poland in 2015.