Marguerite Bay or Margaret Bay is an extensive bay on the west side of the Antarctic Peninsula, which is bounded on the north by Adelaide Island and on the south by Wordie Ice Shelf, George VI Sound and Alexander Island. The mainland coast on the Antarctic Peninsula is Fallières Coast. Islands within the bay include Pourquoi Pas Island, Horseshoe Island and Lagotellerie Island. Marguerite Bay was discovered in 1909 by the French Antarctic Expedition under Dr. Jean-Baptiste Charcot, who named the bay for his wife.