He was the son of William Melmoth the elder and his second wife, Catherine Rolt, was probably born in London, and was baptised in 1710.

[3] At the close of the 18th century, Melmoth was a familiar figure in Bath literary society.

There was a Latin epitaph placed on a tablet in Bath Abbey; but Melmoth was buried at Batheaston.

The Travels in Switzerland of William Coxe consists of letters addressed to him in the late 1770s.

Thomas De Quincey, who was offered a chance to view his manuscripts around 1813, opined that "Melmoth was a fribble in literature".