Tadeusz Peiper (Kraków, May 3, 1891 – November 10, 1969, Warsaw) was a Polish poet, art critic, theoretician of literature and one of the precursors of the avant-garde movement in Polish poetry. Born to a Jewish family, Peiper converted to Catholicism as a young man and spent several years in Spain. He is notable as the co-founder of the Awangarda krakowska group of writers.

Peiper was born May 3, 1891 in Kraków under Partitions. In 1921, in reborn Poland he founded the Zwrotnica monthly (a "Railroad switch"), devoted mostly to avant-garde movements in contemporary poetry. Although short-lived, the magazine (issued until 1923 and then briefly reactivated between 1926 and 1927), paved the way for the young poets of the Awangarda krakowska (Kraków Avant-garde) group, among them Julian Przyboś, Jan Brzękowski and Jalu Kurek. He also published three notable collections of poems, all of them being among the most notable pieces of the constructivist Polish poetry. As an artist, Peiper believed that a writer should resemble a skilled craftsman, able to carefully plan his words. He also coined the "3 x M" slogan (Miasto, Masa, Maszyna; Polish for City, Mass and Machine), one of the memes of Polish poetry of the 1920s. Soon after World War II he wrote about Mickiewicz for Tygodnik Powszechny. Until retirement, Peiper worked for Jerzy Borejsza.