Sharpe's Waterloo is a historical novel in the Richard Sharpe series by Bernard Cornwell. Originally published in 1990 under the title Waterloo, it is the eleventh novel of the Sharpe series and the twentieth novel in chronological order. Cornwell stated that he intended to end the series here, but later changed his mind.^{[citation needed]}

Napoleon having escaped from Elba, Richard Sharpe leaves his farm in Normandy to rejoin the British Army, accompanied by his lover Lucille. He is hired by the Prince of Orange as part of his staff and appointed a lieutenant colonel. Sharpe's friend Patrick Harper, despite being a civilian who has ostensibly come to Belgium to trade in horses, resumes his old place at Sharpe's side.

While patrolling the roads connecting the Anglo-Dutch and Prussian forces, Sharpe sees a large unit of Napoleon's Army of the North crossing the border from France, revealing that Napoleon does not intend to maneuver around the flank of the allied armies via Mons, as the Duke of Wellington expects, but instead to drive into the gap between the British and Prussian armies and defeat them in detail. Sharpe sends an urgent message to General Dornberg, while he stays behind to continue observing the French. Unfortunately, Dornberg thinks it is a French ruse and tears it up.

Later that day, after the French have entered Charleroi, Sharpe returns to the Prince of Orange's headquarters and is aghast to find that the army is ignorant of the French invasion. The Prince's Chief of Staff, Baron Rebecque, despatches a messenger to retrieve the Prince from Brussels, while Sharpe carries orders to the troops nearest to the crossroads at Quatre Bras, commanded by Prince Bernhard Carl of Saxe-Weimar-Eisenach. Although the French are checked as evening falls, Sharpe knows they will launch a much stronger attack in the morning, and rides to Brussels to warn Wellington.

Sharpe barges into the Duchess of Richmond's ball and informs Wellington. Wellington is dismayed at being "humbugged" by Napoleon. At the ball, Sharpe is outraged to encounter Lord John Rossendale, the lover of his estranged wife Jane. Rossendale flees, but Sharpe catches him in full view of the guests. He insults Rossendale, offers to settle matters with a duel, and demands the return of the money Jane stole from him. Rossendale, knowing full well that he would lose a duel with Sharpe, meekly acquiesces, but Jane obliquely encourages him to use the impending battle as a cover to kill Sharpe.

At Quatre Bras, a Belgian unit brought up to reinforce Saxe-Weimar breaks and runs as soon as the first French column appears (the Belgians having recently been French allies). The Prince of Orange twice attempts to lead a charge of his Dutch-Belgian cavalry against an opposing force of French lancers, but his men refuse to follow him.

Wellington arrives at Quatre Bras in time to see the Belgian troops fleeing, and details General Picton to deploy the British reinforcements, while Wellington rides east to confer with the Prussians. The Prince of Orange, humiliated by his own troops' poor performance, becomes outraged at Picton deploying brigades from I Corps, of which the Prince is the nominal commander, without consulting him. The Prince orders General Halkett's brigade to form line and advance. The Prince disregards Sharpe's warning that the French cavalry are lurking nearby and will massacre any infantry in line, and dismisses Sharpe from his staff when Sharpe refuses to deliver the orders to Halkett.

The 69th Regiment obeys and is all but wiped out by cavalry led by General Kellermann. Sharpe and Harper rush to the side of their old regiment, the Prince of Wales' Own Volunteers, and save some of them by urging them to flee to the safety of a forest. The brigade takes heavy casualties, and the French cavalry capture the 69th's King's Colour. Although more reinforcements arrive in time to check the French advance, Sharpe rages at the needless loss of life caused by the Prince.