Impressment is the act of forcibly conscripting people to serve as sailors. It was much used by the Royal Navy during the 18th century and early 19th century as a means of crewing warships, although legal sanction for the practice goes back to the time of King Edward I. The Royal Navy impressed many British sailors, as well as countless sailors from other nations of the world during the 1700s and the early 1800s. People eligible for impressment were eligible men of seafaring habits between the ages of 18 and 55 years with a few exceptions which were not always honoured.

Conditions for the average sailor in the Royal Navy were very bad, and pay was low. Especially during wartime, it was impossible to fully staff the Navy with volunteers, a problem worsened by desertion. The Impress Service was formed to force sailors to join the navy, based legally on the power of the King to call men to military service. The Impress Service in turn utilized "press gangs" to do the convincing, duping, kidnapping, or otherwise forcing sailors into Navy service. Corruption was rife, as press gangs could be bribed in order to bypass a "candidate".

Impressment was criticized as oppressive and unjust, but was tolerated for over a century in Britain due to the necessity of crewing the Royal Navy with England under constant threat of invasion from the continent.

In the late 1700s and early 1800s, the Royal Navy aggressively reclaimed British deserters posing as sailors of any other Navy, both by halting and searching merchant ships, and in many cases, by searching American port cities. Since it was difficult to tell whether a sailor was British or American, the Royal Navy "accidentally" impressed over 6000 American sailors during the early 1800s. This was one of the factors leading to the War of 1812 in North America.

In 1794, the Jay Treaty was ratified by Congress. The treaty, negotiated with Britain by John Jay, defused a situation that could have led to war. However, the treaty neglected to address British impressment of American sailors which caused many American citizens to disapprove greatly. This controversy was one of the main factors that led to the emergence of political parties.

British impressment ended in practice after 1815. The last law concerning impressment was passed in 1835, and limited the length of service of a pressed man to five years and added the proviso that a man could not be pressed twice. The various laws authorising impressment have not been repealed.