The Richmond–Petersburg Campaign is a series of battles around Petersburg, Virginia, fought from June 9, 1864, to March 25, 1865, during the American Civil War.

Although it is more popularly known as the Siege of Petersburg, it is not a classic military siege, in which a city is usually surrounded and all supply lines are cut off, nor is it strictly limited to actions against Petersburg.

The campaign is nine months of trench warfare in which Union forces commanded by Lt. Gen. Ulysses S. Grant assault Petersburg unsuccessfully and then construct trench lines that eventually extend over 30 miles (48 km) from the eastern outskirts of Richmond, Virginia, to around the eastern and southern outskirts of Petersburg.

Petersburg is crucial to the supply of Confederate Gen. Robert E. Lee's army and the Confederate capital of Richmond.

Numerous raids are conducted and battles fought in attempts to cut off the railroad supply lines through Petersburg to Richmond, and many of these cause the lengthening of the trench lines, overloading dwindling Confederate resources.Lee finally yields to the overwhelming pressure—the point at which supply lines are finally cut and a true siege would have begun—and abandons both cities in April 1865, leading to his retreat and surrender at Appomattox Court House.

The Siege of Petersburg foreshadows the trench warfare that is common in the First World War, earning it a prominent position in military history.

It also features the war's largest concentration of African American troops, who suffer heavy casualties at such engagements as the Battle of the Crater and Chaffin's Farm.