Elvi Svendsen, later Carlsen (January 8, 1920 – February 7, 2013) was a Danish backstroke and freestyle swimmer who competed in the 1936 Summer Olympics and in the 1948 Summer Olympics. She was born in Copenhagen. She was the daughter-in-law of Carl Carlsen and the sister-in-law of Inger Carlsen. In 1936 she was a member of the Danish relay team which finished seventh in the 4×100 metre freestyle relay event. In the 100 metre freestyle competition she was eliminated in the first round.