John Petre, 1st Baron Petre (20 December 1549 – 11 October 1613) was an English peer.
John was the only surviving son of the statesman Sir William Petre by his second wife Anne Browne, daughter of Sir William Browne, Lord Mayor of London. A talented amateur musician, he kept a full set of musical instruments (lute, five viols, virginals and organ) and was a patron of the composer William Byrd, a fellow catholic who lived at nearby Stondon Massey. On several occasions, Byrd brought a group of musicians to Ingatestone to entertain at Christmas and dedicated a collection of his Graduale settings to Lord Petre. John Petre was not endowed with the ability of his father and a much less forceful character but being a diligent landowner, public figure and a competent musician along with his great possessions and his father’s fame served him well. We know little more about him. Like his descendants, he was a Roman Catholic, but he must have kept his religious opinions in the background, or James would hardly have made him a peer.
In 1570, he married Mary (died 2 August 1604), eldest daughter of Sir Edward ‘Walgrave’ (or Waldegrave) of Borley. By the time of her marriage, Mary was fatherless and poor but gave her parents-in-law ‘much joy in his choice’. She left four sons, of whom the eldest, William, 2nd Lord Petre, was father of William Petre (1602–1677). He probably erected the beautiful recumbent tomb of Sir William, and is himself commemorated by the magnificent one in the north chapel, now the vestry.
When Sir William died in 1572, his widow continued to reside at Ingatestone Hall, and so John and wife Mary Waldegrave, then resident at Writtle Park, looked for another property to suit their status. In 1574, John added West Thorndon Hall and a further 12,000 acres (49 km2) to the family estate, which became the principal seat of the family.
He was knighted, in 1576, by Elizabeth after his father’s death. The domestic papers of Queen Elizabeth’s time not infrequently notice Sir John. Despite his Catholic attitudes, he held a number of local offices in Essex, as JP, sheriff (1575-6), and deputy lieutenant (1590–98). He was also MP for Essex in the Parliaments of 1584–5 and 1586-7. In 1603 he was raised to the peerage as Baron Petre, of Writtle in the County of Essex. He publicly acknowledged that he was a Roman Catholic and his descendants have remained loyal to Catholicism ever since.