John-Paul Knowlson and Stuart O'Neill absconded from HMP Leyhill in south Gloucestershire around 2am on Wednesday.
Knowlson, 30, is from Bristol and was convicted of rape in 2011 at Bristol Crown Court.
He is described as white, 5ft5in tall and of medium build with brown eyes.
Last seen wearing a red tracksuit top, Knowlson speaks with a West Country accent and has a tattoo of a cross on his right arm.
O'Neill, 29, is from the Lancashire area with strong links to Manchester and was convicted of rape, burglary and theft offences at Manchester Crown Court in 2009.
He is white, 6ft1in tall and of medium build with blue eyes and a beard.
O'Neill speaks with a Mancunian accent and has a tattoo with his surname on the base of his neck.