Jānis Alksnis (7 December 1869 – 9 January 1939) was a Latvian architect.
Alksnis was born in Taurene parish in Latvia. He was autodidact, and was granted a builder's license in 1901. He was then very active for a rather short period of time, coinciding with rapid economic growth in Riga. Between 1901 and the outbreak of World War I, he designed more than 130 private and public buildings in Riga, most of them in Art Nouveau style. He died in Riga.