Born June 18, 1799, in Bolton, Lancashire; died Oct. 5, 1880, in Maidenhead. British astronomer-observer. Member of the London Royal Society (from 1849); president of the Royal Astronomical Society from 1870 to 1872.
In 1844–46, Lassell constructed a 2-ft reflector with the help of which he discovered in 1846 a satellite of Neptune, and in 1851, a third and fourth satellite of Uranus. In 1851 he moved to the island of Malta, where in 1861 he constructed a 4-ft reflector. In 1867, Lassell published a catalog of 600 nebulae discovered using this reflector.