HMS Hood (pennant number 51) was the last battlecruiser of the Royal Navy to be built. One of four Admiral-class battlecruisers ordered in mid-1916 under the Emergency War Programme, her design—although drastically revised after the Battle of Jutland and improved while she was under construction—still had serious limitations. For this reason, and since the German battlecruisers they were designed to counter were unlikely to be completed, work on her sister ships was suspended in 1917 leaving Hood as the only one to be constructed. She was named after the 18th-century Admiral Samuel Hood.
Hood was involved in a number of flag waving exercises between her commissioning in 1920 and the outbreak of war in 1939; these included sorties to the Mediterranean Sea and a circumnavigation of the globe with the 1st Light Cruiser Squadron in 1923–24. She was refitted twice before being stationed with the Mediterranean Fleet due to the outbreak of the Second Italo-Abyssinian War. When the Spanish Civil War broke out she was officially assigned to the Mediterranean Fleet; returning to England in 1939 for an overhaul. At this point in her service, Hood's usefulness had deteriorated due to changing technology in the naval armour and weaponry. While she was scheduled to undergo a major rebuild in 1941 to correct these issues, the outbreak of the Second World War resulted in her being pressed into service without the upgrades she needed.