Norris, Sir Thomas (1556–99), soldier and president of Munster, was fifth son of Henry Norris, 1st Baron Norris of Rycote, Oxfordshire, and his wife Margaret, daughter of John Williams, 1st Baron Williams of Thame, and was a younger brother of Sir John Norris (qv). He attended Magdalen College, Oxford, and graduated on 6 April 1576. In December 1579 he came to Ireland as a captain of horse in the Munster campaign against Gerald Fitzgerald (qv), earl of Desmond. Temporarily appointed governor in Connacht in the winter of 1580–81, he soon returned to Munster, where he forced Desmond to raise his siege of Dingle in December 1581.
On the retirement of Capt. John Zouche (August 1582), Norris was appointed colonel of the forces in Munster despite some official reservations about his youth, the indiscipline of his troops, and his short temper. He was relieved of this command when the earl of Ormond (qv) was appointed governor of Munster in December 1583. After a brief visit to England, he was sent to the north to resolve a dispute between Hugh Oge O'Neill and Shane MacBrian O'Neill over possession of the castle of Edendougher. His delivery of the castle to Shane accorded with official policy and he was commended for his tact and discretion. In the autumn he accompanied his brother John, newly appointed president of Munster, and the new lord deputy, Sir John Perrot (qv), on an expedition against the Scots in Antrim, in which he was wounded in the knee by an arrow.
Norris returned to Munster in December 1584, having been appointed vice-president to his brother John. On 24 April 1585, the eve of the meeting of the Irish parliament, to which he had been returned for Co. Limerick, he was appointed deputy during John's absence in the Netherlands. After the parliamentary attainder of the earl of Desmond (1586), Norris was appointed to the commission for surveying the escheated lands. And after the withdrawal of the original grantee, Sir John Popham, he acquired the 6,000-acre seignory of Mallow, on the development of which (according to his widow) he invested £5,000. His administration was a troubled one: the disorders caused by dispossessed proprietors attempting to recover their estates were matched by the disturbances caused by unruly undertakers and settlers attempting to take over land that had not been escheated, and by undertakers encroaching on each other's seignories. His fellow undertakers regarded him as unduly favouring the original proprietors, particularly those who had received pardons before the passage of the acts of attainder, and constantly criticised the conduct of his soldiers. He made little progress in settling his own undertaking, though he established an ironworks.
After he was knighted by the lord deputy, Fitzwilliam (qv), in December 1588, fresh troubles beset him as fears of Spanish invasion mounted. Under the direction of his brother John, who returned to Ireland for the purpose in 1590, he improved the fortifications at Limerick, Waterford, and Dungannon, but he lacked the soldiers and equipment to garrison them. In 1590 his soldiers mutinied and marched to Dublin to demand that they be paid. As a last resort, he suggested that some of the most trusted noblemen should be armed ‘in the Irish fashion’ for the defence of the province. Norris was appointed as head of the commission set up in 1592 to adjudicate the outstanding land disputes. The terms of reference stressed the importance of placating the province, and Norris and his fellow commissioners followed their instructions with a fidelity that encouraged a wave of claims for the resumption of confiscated land during the following six years, many of them successful.
In June 1594 Norris left Munster to accompany the new lord deputy, Sir William Russell (qv), on his journey through Ulster. He returned again to Ulster in the following year, serving under his brother John against the earl of Tyrone (qv) and was wounded in the thigh. During his absence the first attacks on English settlers took place in Munster, and Russell (whose animosity towards John Norris was undisguised) accused Thomas of neglecting his charge there. Norris returned to Munster and was engaged throughout 1596 in repelling raids from the MacSheedys and the O'Briens. In August he reported that in ten days he had hanged upwards of ninety of them. He was criticised during this period for trying to enforce compulsory attendance at divine service. On Sir John's death in July 1597, Norris was appointed to succeed him as president of Munster; on the death of the lord deputy, Lord Burgh (qv), he was chosen sole lord justice of Ireland by the Irish council on 29 October. On 15 November, however, Elizabeth ordered him back to Munster and instructed the council to replace him with the lord chancellor, Archbishop Adam Loftus (qv), and the chief justice, Sir Richard Gardiner.
When the Munster rising began on 4 October 1598, Norris's force was seriously under strength, the undertakers were able to provide only token support, and he was obliged to withdraw to Cork. An alarmed English government undertook to send munitions, victuals, and 2,000 foot soldiers as soon as they could be mustered and transported. Complaints from his settler critics had already reached the court, and the queen was persuaded that the retreat to Cork had been premature and cowardly. When the promised force arrived at the beginning of December, Norris set out to regain control and, despite a severe shortage of supplies, succeeded in relieving Killmallock and (in March 1599) Rosscarbery. In May, after the earl of Essex (qv) arrived on Ireland as lord lieutenant with fresh forces, Norris went to meet him in Kilkenny to arrange to accompany him on his Munster expedition. Shortly afterwards, on a march to revictual the garrison in Limerick, Norris was wounded in the head in a skirmish with the Burkes of Castleconnell. He completed his journey before taking to his sickbed in Kilmallock, where Essex visited him to seek advice, and recovered sufficiently to join Essex for part of the campaign. His condition deteriorated, however, and he was taken home to Mallow, where he died on 20 August 1599.
His brother Henry had died of injuries received in the campaign some two months previously. He was survived by his wife Bridget, daughter of Sir William Kingsmill of Sydmonton, Hampshire, who became a catholic in 1602, and their only child, Elizabeth, who married Sir John Jephson of Froyle, Hampshire, captain in the army in Ireland.