The Cruel Sea is a 1951 novel by Nicholas Monsarrat. It follows the lives of a group of Royal Navy sailors fighting the Battle of the Atlantic during World War II. It contains seven chapters, each describing a year during the war.

The novel, based on the author's experience of serving in corvettes in the North Atlantic in World War II, gives a matter-of-fact but moving portrayal of ordinary men learning to fight and survive in a violent, exhausting battle against the elements and a ruthless enemy.

Few books have ever conveyed in such gripping detail the brutal destruction of the Battle of the Atlantic and the endurance of the men who fought it. The novel brought instant fame to its author.