Carl Barnett Allendoerfer (April 4, 1911 – September 29, 1974) was an American mathematician in the mid-twentieth century, known for his work in topology and mathematics education.

Allendoerfer was president of the Mathematical Association of America (1959–60) and editor of its monthly journal.

After his death, the MAA established the Carl B. Allendoerfer Award, which is given each year for "expository excellence published in Mathematics Magazine."

Allendoerfer is also known as a proponent of the New Math movement in the 1950s and 1960s, which sought to improve American primary and secondary mathematics education by teaching abstract concepts like set theory early in the curriculum.

The commission and report were criticized by some for emphasizing pure mathematics in place of more traditional and practical considerations like arithmetic.