Sigma Delta Rho (ΣΔΡ) was a fraternity formerly active at Amherst College that eventually affiliated with Theta Xi before reverting to local status as Alpha Theta Xi, thereafter becoming defunct as a chapter but continuing as a co-ed cooperative.

The fraternity was founded in 1909 as the result of a membership split in the Hitchcock Club, a local campus literary society.

In 1913 the fraternity purchased and moved into a property which it continued to occupy until 1924 before acquiring a new house at 62 Snell Street.

[2] In 1932 Sigma Delta Rho affiliated with Theta Xi, becoming that fraternity's Alpha Mu chapter.

[4] By the 1970s, according to one account, the group had started to attract "nonconformists" and "seemed to morph into a sort of counterculture theme house, merely going through the motions of being a fraternity.