Lewis Albert "Lew" Johnstone (5 April 1916 – 11 May 1983) was an Australian politician. He was a Labor member of the New South Wales Legislative Assembly, representing Cobar from 1965 to 1968 and Broken Hill from 1968 to 1981.Johnstone was born in Broken Hill to Charles Albert Johnstone, an underground mine manager, and Jessie Charlott Thueff. He was educated at public schools in the area and studied mine draughting and engineering.