Aylmer, Matthew (c.1650–1720), 1st Baron Aylmer of Balrath , admiral, and commander-in-chief of the fleet, was second child and second son among three sons and one daughter of Christopher Aylmer (d. 1671), 1st baronet, of Balrath, Co. Meath, and his wife Margaret, third daughter of Matthew Plunkett, 5th Lord Louth. Employed to recruit soldiers in Munster, and proving unsuccessful, he distinguished himself c.1676 when he and his brother Gerald, at their own expense, recruited and transported 160 soldiers to Holland to fight against the French. Under the patronage of the duke of Buckingham (1628–78), he entered the navy as a lieutenant (1678), was promoted captain (1679), and served in the Mediterranean.
It was probably while serving in Holland that he gained his admiration for William of Orange (qv), which inspired him to join the revolution of 1688 and become involved in intrigues and negotiations to secure the loyalty of the English fleet for William, for whom he acted as envoy. After the battles of Beachy Head (1690) and La Hogue (1693), he was promoted rear-admiral (1693) and vice-admiral (1693). As commander of the navy (1694–1702) he skilfully concluded treaties with the regencies of Tunis, Tripoli, and Algiers in 1698. The following year, for reasons not entirely clear, he was superseded as vice-admiral and retired from active service; he was made governor of Deal castle and remained a commissioner of the navy till 1702.
He entered parliament on the admiralty interest, representing first Portsmouth (1695) then Dover (1697–1713, 1715–18, 1720). A dedicated whig – described by Jonathan Swift (qv) as ‘a virulent party man, born in Ireland’ (Sedgewick, 426) – he was appointed commander-in-chief of the fleet (1709–11). With the return of the whigs to power, he was appointed admiral and commander-in-chief of the fleet (1714–18), ranger of Greenwich Park, and governor of the Royal Hospital of Greenwich, London (1714), where he founded the hospital school for sons of seamen. Serving as lord of the admiralty (1717–18) – he was succeeded on the admiralty board by his son-in-law, Sir John Norris (1671–1749) – he was appointed a rear-admiral of Great Britain (1717–20) and created baron of Balrath in 1718. He died 18 August 1720 in Queen's House, Greenwich, and is buried in Greenwich church.
He married (c.1677) Sarah Ellis (d. 1710); they had one son – Henry, 2nd baron – and three daughters. Two three-quarter-length portraits of Aylmer are in the National Maritime Museum, Greenwich: one after Sir Peter Lely, showing Aylmer as a young man, and one (c.1692–3) by Jonathan Richardson.