Andreas Heusler (10 August 1865 in Basel – 28 February 1940 in Basel) was a Swiss medievalist, specialising in Germanic and Norse studies.
Andreas Heusler was born into a prestigious family in Basel, the third in a line of fathers and sons bearing the same name (his father was Andreas Heusler (1834–1921) and his grandfather Andreas Heusler (1802–1868); both worked in law and government). Andreas enjoyed a stellar career as a student in Basel, Freiburg im Breisgau, and Berlin, completing his studies in 1887 in Freiburg with the doctoral thesis "Beitrag zum Consonantismus der Mundart von Baselstadt".
In 1890, when Heusler was 25 years old, he began lecturing in Berlin and was a professor of Nordic textual studies there from 1894 to 1913. He focused on research into Old Norse literature, especially the Poetic Edda and Íslendingasögur, translating many works into German and travelling twice to Iceland. From 1914 to 1919, Heusler was professor of Germanic textual studies at Berlin University. He moved back to Switzerland in 1920 and lived in Arlesheim near Basel, where a place was made for him at Basel University, where he worked until he reached the age limit in 1936.
Besides ancient Germanic and Nordic culture, Heusler was noted for his love of music (he played the violin); around 1889 he switched from a strongly held Christianity to being a confirmed atheist. There is some debate as to where Heusler stood on German nationalism in the 1930s. He seemes at first to have been swayed by it, but it is thought that he turned his back on Adolf Hitler around 1938. A good insight into his thoughts is offered by the four hundred letters to Wilhelm Ranisch which he wrote in the period 1890–1940.