Brownlow, William (1726–94), MP and landowner, was born 10 April 1726, son of William Brownlow (1683–1739), landowner and MP, for Co. Armagh (1711–27), and Lady Elizabeth Brownlow of Co. Armagh, and grandson of Arthur Brownlow (qv). His mother was a daughter of James Hamilton (qv), 6th earl of Abercorn. He inherited the family estates round Lurgan in 1739, and spent some of his youth in France and Italy with his mother.
His father, grandfather, and great-grandfather had been MPs, and in 1753 Brownlow won a hotly contested by-election in which his opponents accused him of papist and Jacobite sympathies. The unsuccessful candidate was Francis Caulfeild, brother of James, 1st earl of Charlemont (qv); his petition to parliament caused a furore and was lost by only one vote in one of the most celebrated electoral struggles of the day. Brownlow represented the county from 1753 until his death – over forty years. In 1753 he supported the government on the controversial money bill.
He married (25 May 1754) Judith, daughter of the Rev. Charles Meredyth of Meath, dean of Ardfert; they had two sons. After her death (October 1763) in Lyons, France, he married (25 November 1765) Catherine, daughter of Roger Hall of Newry, Co. Down, and had two more sons and five daughters; three married into the nobility. In 1758 he was one of the wide streets commissioners in Dublin, and owned an imposing house in Merrion Square. He was a trustee of the linen board in Ulster, and made many improvements to his estate, castle, and demesne, the local church, and the town of Lurgan; however, it was alleged that private roads in his demesne were built with public money. He was one of a few landowners in Armagh who were believed to have misappropriated the unusually high county cess levied by the grand jury, of which he was a member. He suggested (1758) that salaries be paid to government officials, and one official, Henry Meredyth (d. 1789), his first wife's uncle, subsequently received an annual salary of £500.
In June 1763 large numbers of presbyterian farmers and weavers, calling themselves the Hearts of Oak, in a notable show of dissatisfaction with the privileges of landlords, marched on the homes of the gentry to demand redress. Brownlow was in England, and avoided a confrontation. Despite the allegations of abuse of public money, Brownlow was generally recognised as one of the more independent and reform-minded MPs of the day. He captained a Volunteer troop of dragoons which marched from Lurgan to assist Belfast after the French commander François Thurot (1727–60) landed at Carrickfergus in 1760; and as one of the supporters of Henry Grattan (qv), he was prominent in the Volunteer movement of the 1780s. He was captain of the Lurgan Volunteer company and lieutenant-colonel of the northern battalion, and backed the movement in parliament until displeased by the Volunteer national convention (10 November–2 December 1783), which sought franchise reform and seemed to challenge the authority of the existing parliament.
He subscribed £9,000 to help found the Bank of Ireland (1783), and in parliament on 7 February 1785 vigorously opposed Pitt's proposals on Ireland's commercial relations with England, seeing in them the danger that Ireland would become a ‘tributary nation’. He was appointed a privy councillor in 1765. He organised horse races in his locality, and was a talented harpsichord player. After his death (28 October 1794) the Belfast News Letter printed an unusually long and glowing tribute, expressing admiration for his ‘incorruptible integrity’ and patriotism, as well as two poetic elegies. He was succeeded by his son William Brownlow (qv).