Johannes Vahlen (September 27, 1830, Bonn – November 30, 1911, Berlin) was a German classical philologist. He was the father of mathematician Theodor Vahlen (1869-1945).
In 1852 he graduated at the University of Bonn, where he studied classical philology. In 1856 he became an associate professor at the University of Breslau, and in 1858 a full professor at the University of Freiburg. Shortly afterwards he relocated to Vienna, where in 1862 he became a member of the Vienna Academy of Sciences. Beginning in 1874 he was a professor of classical philology at the University of Berlin, where he was also a member of the Prussian Academy of Sciences.
Vahlen was a specialist of Greek and Latin literature, and published works on a wide array of ancient authors that included Aristotle, Ennius, Horace, Plautus and Gnaeus Naevius. He is particularly known for his interpretive work involving the Poetics of Aristotle and the fragmentary relics of the poet Ennius; Ennianae poesis reliquiae.
In 1913 Vahlen's library of over 10,000 volumes of ancient and classical works were acquired by the University of Illinois.