Ontario Provincial Police say the banner was stolen from the Whitecap Pavilion in Kenora, Ont., sometime between Friday evening and Saturday morning.
The burgundy and white banner is about two metres long and a little under a metre wide.
The Kenora Thistles defeated the Montreal Wanderers to win the Stanley Cup in 1907.
Police say a Canadian flag and a Los Angeles Kings Stanley Cup flag were also stolen.
Anyone with information is asked to contact provincial police or Crime Stoppers.