Gilbert, Claudius (d. c.1696), clergyman and pamphleteer, may have been related to a Claudius Gilbert who applied for naturalisation in England in 1656, and who may have been French. Alexander Gilbert, a commonwealth minister in the diocese of Connor in 1655, could have been a brother. Claudius Gilbert was a nephew, or nephew by marriage, of Henry Markham, a Cromwellian colonel who was granted lands in Ireland. Gilbert was educated at St Catherine's College, Cambridge, where he was admitted as a pensioner (1642), and graduated BA (1648). In 1655 TCD granted him the degree of BD. He had been in Ireland since 1652, when he was installed in Limerick as a minister under the commonwealth at a salary of £200 a year – one of the highest salaries paid to ministers in Ireland, and equal to that of men who had formerly been bishops.
A forceful opponent of quakers and baptists, Gilbert's views were strongly presbyterian, in the English rather than the Scottish tradition. In 1655 he was appointed to committees dealing with the choice of new fellows in TCD and the approbation of ministers in Co. Cork and in 1658 he and Thomas Harrison (qv) presented a report denouncing thirty-one ministers as scandalous or inefficient. Gilbert supported Edward Worth's (qv) plan to introduce order to the church in Ireland and published (1657–8) four pamphlets on religio-political topics, in which he argued for the intervention of the civil power in religious matters. The approval of the lord deputy, Henry Cromwell (qv), was signified by his appointment as minister of St Michael's, Dublin, in 1658; he had relinquished this post by April 1660. He conformed to the Church of Ireland after the restoration of Charles II, though with little pretence of having changed his opinions. He moved north to become prebendary of Ballymore in the diocese of Armagh (1666–8), and through the patronage of Arthur Chichester (qv), 1st earl of Donegall, who was sympathetic to dissenters and later left money to Gilbert in his will, became vicar of Belfast (1668–95).
Gilbert seems to have continued to use the non-episcopal titles of minister and ‘theologian of Belfast’ (as in his son's TCD entrance record), and he was apparently tolerant of the presbyterians in the town. He even permitted Thomas Emlyn (1663–1741), who was already markedly nonconformist, to preach in the parish church. Gilbert was concurrently rector of Drumbeg, Co. Down, from 1674. His name occurs in connection with a dispute over the tithes of this small parish, which were paid to him as incumbent – though the archdeacon of Down, Lemuel Mathews (qv), claimed them, possibly correctly, as his perquisite. The archdeacon's servants used violence against some parishioners who supported Gilbert's rights; and a Margaret Lostin, who subsequently died, was said to have appeared to a neighbour as an unquiet ghost seeking redress. Gilbert gave details of the apparition and its outcome in a lawsuit at Downpatrick (1685) to the English presbyterian minister Richard Baxter, who published them in Certainty of the world of spirits (1691). Gilbert seems to have died about 1696.
His will (1690) directed that £20 owed to him by the town of Belfast should be given to the poor, and mentioned his wife Margaret (family name unknown) and his only child, Claudius Gilbert (qv). Some of the books in the younger Gilbert's famous library may have been his father's; the first Claudius is said to have been proficient in Hebrew, Latin, Greek, Arabic, French, Italian, and Spanish.