Rolf Axel "Acke" Ejnar Grönberg (9 May 1918 – 23 April 1988) was a Swedish Greco-Roman wrestler, who won the Greco-Roman middleweight division at the 1948 and 1952 Summer Olympics. Grönberg was raised in Norberg, but moved to Stockholm as a teenager. There he worked as a plumber and masseur, and started wrestling following his elder brothers Fritz and Harald. Besides his Olympic medals he won a world title in 1950, three European Championship medals, as well as 16 national titles between 1944 and 1958.