Cap Diamant ("Cape Diamond") is the official name of the cape and promontory on which Quebec City is located, formed by the confluence of a bend in the St. Lawrence River to the south and east, and the much smaller St. Charles River to the north.

Jacques Cartier, the French explorer who found glittering stones in the high cliff, thought the stones contained diamonds. After he brought samples of these stones back in France in 1542, experts concluded that these "diamonds" were actually quartz, hence the proverb "Faux comme un diamant du Canada" ("as fake (or as false) as a Canadian diamond").