Sir Nicholas Arnold (1507–1580) was an English courtier and politician.
He was the son of John Arnold, Lord of the manor of Highnam and Over, and his wife Isabel Hawkins.
In 1530 he entered the service of Thomas Cromwell and assisted him in the Dissolution of the Monasteries. He was by 1526 a gentleman pensioner of Henry VIII and in 1538 one of the king's bodyguard.
In 1546 he was sent to take charge of the English fort of Boulogneberg near Boulogne in France. In 1549 the fort was attacked by the French but they were completely defeated and Arnold was wounded. After a second attack Arnold realised defence was hopeless and, dismantling the fort, withdrew to Boulogne. He was knighted some time during the reign of Edward VI (c.1553) and spent time travelling in Italy.
He was the Member of Parliament for Gloucestershire in 1545-47, 1553 and 1555. He was later MP for Gloucester in the Parliaments of 1559 and 1563 to 1567 and in 1571 MP for Cricklade. From 1558 to 1580, he was also the Custos Rotulorum of Gloucestershire and in 1558 and 1559 the High Sheriff of Gloucestershire. ]. He was appointed one of the Council of the Marches of Wales in June 1574, and was Lord Deputy of Ireland 1564-65. From 1572 he again served until his death as MP for Gloucestershire.
He was a Protestant and was suspected of involvement with Wyatt's Rebellion.
He married twice:
Firstly Margaret Denys, daughter of Sir William Denys(1470–1533) of Dyrham, Gloucestershire.
Secondly Margaret Isham, daughter and co-heir of John Isham of Bryanstown and widow of Nicholas Hore of Harpersdown, Wexford