Alois Adolf Riehl (German: [ʀiːl]; 27 April 1844 – 21 November 1924) was an Austrian philosopher. He was born in Bozen (Bolzano) in the Austrian Empire (now in Italy).
The brother of Josef Riehl, he was a Neo-Kantian and worked as a professor at Graz, then Freiburg and finally in Berlin, where he commissioned Mies van der Rohe to design his house in Neubabelsberg.
For Riehl, philosophy was not the teaching of Weltanschauung, but principally a criticism of perception.
Riehl died in Berlin and was buried in the Alter Friedhof in Klein-Glienicke.
His wife Sofie, was the aunt of Frieda Gross, the wife of the Austrian medical doctor, scientist and revolutionary, Otto Gross.