Arthur Chichester, 1st Marquess of Donegall (13 June 1739 – 5 January 1799), known as Arthur Chichester until 1757 and as The Earl of Donegall between 1757 and 1791, was an English nobleman and politician in Ireland.

Chichester was born on 13 June 1739. He was the son of Hon. John Chichester and Elizabeth Newdigate (1703–1769), eldest daughter of Sir Richard Newdigate, 3rd Baronet. His paternal grandparents were Arthur Chichester, 3rd Earl of Donegall and Lady Catherine Forbes (a daughter of the 1st Earl of Granard), in 1726.^[1]

He was educated at Westminster School in 1748 and Trinity College, Oxford, matriculating in 1757, before succeeding his uncle in 1757 as fifth Earl of Donegall.^[2]

After taking his seat in the Irish House of Lords in 1765, Donegall served at Westminster as Member of Parliament for Malmesbury (1768–1774) by his friend Lord Suffolk, first following Suffolk and the Grenville group. Reportedly, he never spoke in the House, and did not stand for reelection in 1774.^[2]

As a means of securing his support for the Government in the Irish House of Commons, he was in 1790 created Baron Fisherwick, of Fisherwick in the County of Stafford, in the Peerage of Great Britain. The following year he was also created Earl of Belfast and Marquess of Donegall in the Peerage of Ireland.^[2]

Lord Donegall married three times. On 11 September 1761, he married Lady Anne Hamilton, daughter of James Hamilton, 5th Duke of Hamilton. Before her death on 11 November 1780, they had seven children:

• Lady Charlotte Anne Chichester (b. 1762),^[3] who died in infancy.^[4]
• Lady Henrietta Chichester (b. 1765),^[5] who died in infancy.^[4]
• George Chichester, 2nd Marquess of Donegall (1769–1844), who married Anna May, daughter of Sir Edward May, 2nd Baronet, in 1795.^[4]
• Hon. Arthur Chichester (1771–1788), who died young.^[4]
• Lord Spencer Stanley Chichester (1775–1819), MP for Belfast and Carrickfergus who married Lady Anne Harriet Stewart, daughter of John Stewart, 7th Earl of Galloway, in 1795.^[4]
• Lady Elizabeth Juliana Chichester (d. 1787)^[4]
• Lady Amelia Chichester, who died in infancy.^[4]

On 24 October 1788 he married Charlotte (née Spencer) Moore, daughter of Conway Spencer, and widow of Thomas Moore. She died, without issue, on 19 September 1789.^[4]

In October 1790, he married Barbara Godfrey, daughter of the Rev. Dr. Luke Godfrey, Rector of Midleton, County Cork.^[6]

Lord Donegall held on lease a country residence at Butley Priory, Suffolk. He died on 5 January 1799, aged 59, at his London home in St James's Square, Westminster. His widow, the dowager Marchioness of Donegall, died on 28 December 1829.^[4]