John Gustavus Handcock was an Irish politician.

He was the sixth son of William Handcock

William Handcock (1676–1723)

William Handcock was an Irish politician.He was the eldest son of Thomas Handcock and his wife Dorothy Green. Handcock entered the Irish House of Commons in 1703, representing Athlone until 1714. He sat for Dublin City from 1721 until his death two years later.He married Sarah Warburton, daughter...

 and his wife Susan Warburton, daughter of Richard Warburton. His older brother was William Handcock

William Handcock (1704–1741)

William Handcock was an Irish politician.He was the oldest son of William Handcock and his wife Susan Warburton, daughter of Richard Warburton. His younger brother was John Gustavus Handcock and his cousins were William Handcock, 1st Viscount Castlemaine and Richard Handcock, 2nd Baron Castlemaine...

 and his cousins were William Handcock, 1st Viscount Castlemaine

William Handcock, 1st Viscount Castlemaine

William Handcock, 1st Viscount Castlemaine, PC was an Irish MP and supporter of Union with Great Britain....

 and Richard Handcock, 2nd Baron Castlemaine

Richard Handcock, 2nd Baron Castlemaine

Richard Handcock, 2nd Baron Castlemaine , known as Richard Handcock until 1839, was an Irish peer and politician.-Background and education:...

. In 1761, Handcock entered the Irish House of Commons

Irish House of Commons

The Irish House of Commons was the lower house of the Parliament of Ireland, that existed from 1297 until 1800. The upper house was the House of Lords...

, representing Ballyshannon

Ballyshannon (Parliament of Ireland constituency)

Ballyshannon was a constituency represented in the Irish House of Commons from 1613 to 1800.-Boundaries and Boundary Changes:This constituency was the borough of Ballyshannon in County Donegal...

until his death in 1766.

On 6 August 1755, he married Margaret Caroline Wilson. Their marriage was childless.