Lothar Geitler (18 May 1899 – 1 May 1990) was an Austrian botanist and cytologist.
He was born in Vienna.
His main research interests included blue-green algae (Cyanophyta), diatoms, lichen symbioses and chromosome structure.
The cyanobacteria genus Geitlerinema was named in his honour in 1989.
This article about an Austrian botanist is a stub.