August Christian Valdemar Hassel (9 February 1864 – 30 May 1942) was a Danish sculptor.

Hassel was born in Copenhagen, the son of captain and mechanic Johan Fridolin Hassel and Doris Henriette Eickhoff.

He apprenticed under stucco artist and carver H.C. Berg from August 1879 and graduated from Copenhagen Technical College in January 1882.

He later continued his training at the Royal Danish Academy of Fine Arts where he studied under Theobald Stein, graduating on 30 January 1888.

Hassel had his debut at the Charlottenborg Spring Exhibition in 1888 with a portrait bust of composer Niels Gade.