Ants Piip VR III/1 (28 February 1884, Tuhalaane, Viljandi County, Estonia – 1 October 1942) was an Estonian lawyer, diplomat and politician.

Piip studied at the Teachers' Seminar in Kuldīga (formerly Goldingen), now in Latvia. In 1903–1905, he was a parish clerk and schoolteacher at Alūksne (Alulinn, Marienburg, today in Latvia), also a teacher in the Emperor Nikolai Greek Orthodox Parish School in Kuressaare in 1905–1906, in the Kuressaare Marine School in 1906–1912, and in the Janson Merchant School in St. Petersburg in 1913–1915. He took his High School exams at the Kuressaare State High School, studied at the law department of the St. Petersburg University in 1908–1913, took additional courses in the Berlin University in 1912, received a scientific scholarship from the St. Petersburg University in 1913–1916.

Piip was a member of the Estonian Province Assembly (Eesti Maapäev), and later a member of the Constituent Assembly (Asutav Kogu), and after that, of the Riigikogu. In 1917–1919, Piip was a member of the Estonian Foreign Mission in St. Petersburg and in London, he participated in the Paris Peace Conference. In 1919 he was Deputy to the Minister of Foreign Affairs, 1919–1920 Member of the Estonian delegation in the Tartu peace negotiations between Estonia and the Russian SFSR. In 1919–1940 he was Professor of International Law in Tartu University. In 1920, he was the diplomatic representative the Republic of Estonia in Great Britain. 1920–1921, while Head of State, Piip was also the Minister of War. He held position of Minister of Foreign Affairs five times, also he was in 1923–1925 the Envoy of Estonia to the United States of America. During 1938–1940, Piip was also member of the Riigivolikogu (first chamber of the Riigikogu).