Joseph Leslie Armstrong (27 December 1950 – 20 April 2019) was a British computer scientist. He is best known as one of the co-designers of the Erlang programming language. He was given a Ph.D. in computer science from KTH Royal Institute of Technology (KTH) in Stockholm, Sweden in 2004. He later a professor at KTF from 2014. He was born in Bournemouth, Hampshire.