Adeline Louisa Maria, Countess of Cardigan and Lancastre (24 December 1824, to 25 May 1915), was the second wife of the English peer James Brudenell, 7th Earl of Cardigan and later the wife of the Portuguese nobleman Don António Manuel de Saldanha e Lancastre, Conde de Lancastre. She was the author of scandalous memoirs, My Recollections, published in 1909, under the name Adeline Louisa Maria de Horsey Cardigan and Lancastre, though strictly speaking she was not allowed by the rules governing the British peerage to join her former and current titles together. Her book detailed events and people coupled with gossip concerning the establishment of Victorian England. After her marriage to the Earl of Cardigan in 1858, Queen Victoria had refused to have her at court because Cardigan had left his first wife.
Adeline was born near Berkeley Square, London, the first child and only daughter of Admiral Spencer Horsey Kilderbee and his wife, Lady Louisa Maria Judith (daughter of John Rous, 1st Earl of Stradbroke). From 1832, her father took the surname "de Horsey", after his mother's maiden name. Her younger brothers were Algernon Frederick Rous de Horsey and William Henry Beaumont de Horsey. She made her entry into society in 1842, and became engaged to Infante Carlos, Count of Montemolin, the Carlist claimant to the Spanish throne, in 1848.
Rumours spread after she was frequently seen riding without a chaperone in the company of seventh Earl of Cardigan, who famously led the Charge of the Light Brigade at the Battle of Balaclava in 1854, and was a friend of her father. The Earl was still married to the former Mrs. Elizabeth Tollemache Johnstone, whom Cardigan had married in 1826, after she was divorced by another army officer, Lt. Col. Christian Johnstone, although Cardigan was separated from his wife since 1837. Criticism from her father caused her to leave home in 1857. After a period in a hotel, she took a furnished house in Norfolk Street, Park Lane, and became the Earl of Cardigan's mistress. After the Earl's wife died in July, 1858, the couple sailed away together on the Earl's yacht and married in Gibraltar on 28 September 1858. She was shunned by polite society, but was an accomplished musician and horsewoman, and acknowledged as a leading courtesan. She was left a life interest in the Cardigan estates on her husband's death in March, 1868.