Rudolf Kayser (* 28 November 1889 in Parchim; † 5 February 1964 in New York City) was a German literary historian.

Rudolf Kayser studied literature and received his doctorate with a thesis on Arnim and Brentano.

As a young lecturer at the Berlin Lessing University he made his debut in 1918 with the essay The Intellectuals and the Spiritual.

In 1930 Kayser wrote a biography of his father-in-law, Albert Einstein, under the pseudonym "Anton Reiser".

In 1936, he married Eva Urgiss, daughter of German screenwriter and film critic Julius Urgiß.