Osterman, or Ostermann, is a surname, and may refer to
Alexander Ivanovich Ostermann-Tolstoy
Andrei Osterman
Cat Osterman
Edward Albert Ostermann
Harry Osterman
Ivan Osterman
Lynne Osterman, American politician
Manfred Ostermann (1958–), German local politician (independent) and district chief executive (Landrat)
Max-Hellmuth Ostermann, German World War II Luftwaffe Ace
Jon Osterman, fictional character in the Watchmen series, known more commonly as Doctor Manhattan
J.P. Osterman, Award Winning Author
