The street was laid out in the time of the 4th Earl of Donegall, who was an absentee landlord living in England, considered mentally unfit to manage his affairs (Benn i, pp. 533-34). However, the name Donegall Street does not appear until the time of the 5th Earl of Donegall, his nephew, Arthur Chichester, who succeeded him in 1757. It therefore seems likely that the name honours the 5th Earl, who later became the 1st Marquess of Donegall. Despite also being an absentee landlord, he was more involved in the development of Belfast. He was a peer in the Irish House of Lords. The peerage title refers to the county of Donegall where this family also held lands (in Inishowen).
R M Young summarises the Chichesters' contribution to the development of the town in this period as follows: “In the 18th century the Earls of Donegall improved the town in many respects — a great reclamation was made on the site of Ann Street, and on it the first Linen Hall erected by the estate at a cost of £1, 500. Other public buildings succeeded, including the Exchange (now Belfast Bank), which cost £4,000, and the Parish Church and Vicarage, erected at the sole expense of Lord Donegall. There is a large aquatint in the possession of Robert Macadam, showing the Assembly Room over the Exchange as a richly decorated apartment, and the architect's name is given — Sir R. Taylor. The Brown Linen Hall was followed by the generous gift of the site for the White Linen Hall granted in 1787” (Young, Town Book of the Corporation of Belfast, 1892, p. 333)
Prior to the name Donegall Street becoming established as the sole name, this was known as New Street and also Linenhall Street (one of three streets which had this name at different times). According to Bardon much of it was planned and built by the architect Roger Mulholland in the 1760s (Bardon, Belfast: An Illustrated History, 39-40). It is included in the list of streets in the Belfast Directory 1831-1832.
"Donegall Street (Lower) - This street was laid out in 1754, when the trustees of the Donegall estate made arrangements to open up the undeveloped ground at the north-east of the existing town, and commenced by laying off a new street from what was known as "the four corners", at the foot of North Street. It was afterwards named Linenhall Street, from the new (second) Brown Linen Hall being the first plot to be laid off on it at the corner of Long Lane, then much longer than it is now" (John J Marshall, Belfast Telegraph, 08/01/1941). Marshall also points out that the teacher David Manson gave the address of his school as Donegall Street when he advertised in the Belfast News Letter in 1768, the earliest reference to the name.
There is a blue plaque erected by the Ulster History Circle to commemorate civil engineer William Mulholland (1855-1935) at no. 201, Donegall Street. He is better known in the USA than on this side of the Atlantic, especially for his role in supplying water to the city of Los Angeles. The Mulholland Aqueduct and the road Mulholland Drive are named after him. The latter is a long road through the Santa Monica Mountains, well known as a scenic route and address of the rich and famous, such as Jack Nicholson. David Lynch's noir mystery movie Mulholland Drive (2000) gets its title from this road.