Sir Leonard Greenwell, KCB KCH (1781–1844) was a British Major-general. Greenwell was born in 1781, the third son of Joshua Greenwell of Kibblesworth, of the family of Greenwell of , county Durham. He entered the army by purchase as Ensign in the 45th Regiment of Foot in 1802, became Lieutenant in 1803, and Captain in 1804. In 1806, he embarked with his regiment in the secret British invasion of South America under General Craufurd, which ultimately was sent to La Plata as a reinforcement, and took part in the operations against Buenos Aires. He landed with the regiment in Portugal on 1 August 1808, and, save on two occasions when absent on account of wounds, was present with it throughout the Peninsular War from Roliça to Toulouse.