Lawrence Parsons, 4th Earl of Rosse, KP FRS (17 November 1840 – 29 August 1908) was a member of the Irish peerage and an amateur astronomer.

He was born at Birr Castle, Parsonstown, King's County, Ireland, the son and heir of the astronomer William Parsons, 3rd Earl of Rosse who built the "Leviathan of Parsonstown" telescope, largest of its day, and his wife, the Countess of Rosse (née Mary Field), an amateur astronomer and pioneering photographer.

Lawrence succeeded his father in 1867 and was educated first at home by tutors, like John Purser, and after at Trinity College Dublin and Oxford University.

Lord Rosse also performed some preliminary work in association with the practices of the electrodeposition of copper sulfate upon silver films circa 1865 whilst in search of the design for a truly flat mirror to use in a telescope.

[3] He revived discussion in on his work Nature's August 1908 edition after witnessing similar techniques used to present newly devised searchlights before the Royal Society.