William Longworth (26 September 1892 – 19 October 1969) was an Australian freestyle swimmer who competed for Australasia in the 1912 Summer Olympics.
He was born in Rixs Creek, Singleton, New South Wales and died in Wahroonga, New South Wales.
In 1912 he qualified for the final of the 100 metre freestyle event as well as for the semi-finals of the 1500 metre freestyle competition but due to illness he was unable to continue competing.