Adeliza of Leuven (1103-1151), also called Adela and Aleidis, was queen consort of England from 1121 to 1135, the second wife of King Henry I of England. She was the daughter of Godfrey I of Leuven, Duke of Lower Lotharingia, Landgrave of Brabant and Count of Leuven and Brussels.
She married King Henry I in 1121 when she is thought to have been aged somewhere between fifteen and eighteen. Her husband was fifty three. It is believed that Henry's only reason for marrying again was his desire for a male heir. Despite holding the record for the largest number of illegitimate children of any British monarch, William Adelin was Henry's only legitimate male heir and had predeceased his father on 25 November 1120. Adeliza was reputably quite pretty and her father was Duke of Lower Lotharingia. These were the likely reasons she was chosen. However, no children were born during the almost 15 years of the marriage.

Adeliza, unlike the other Anglo-Norman queens, played little part in the public life of the realm during her tenure as queen consort. Whether this is because of personal inclination, or because Henry preferred to keep her nearby in hopes of her conceiving, is unknown and probably unknowable. She did, however, leave a mark as a patron of literature and several works, including a bestiary, were dedicated to her. She is said to have commissioned a verse biography of King Henry; if she did it is no longer extant.

When her husband died on 1 December, 1135, Adeliza retired for a while to the monastery of Wilton, near Salisbury. As she was still young she came out of mourning some time before 1139 and married William d'Aubigny, 1st Earl of Arundel, who had been one of Henry's chief advisors. She brought with her a queen's dowry, including the great castle of Arundel, and Stephen of England created d'Albini Earl of Arundel and Earl of Lincoln. Although her husband was a staunch supporter of King Stephen during the Anglo-Norman civil war, her own personal inclination may have been toward the cause of her step-daughter Matilda, known as the Empress. When the Empress sailed for England in 1139, it was to her step-mother that she appealed for shelter, and she landed near Arundel and was recieved as a guest of the former queen.

Adeliza spent her final years in the abbey of Affligem (Landgraviat of Brabant, German Empire), where she died on April 23, 1151. She was buried in the abbey church next to her father, duke Godfrey I of Leuven.