Which of the following was the first planet discovered with the help of a telescope?

Uranus was the first planet discovered with the help of a telescope. William Herschel discovered it in 1781 using a telescope he built himself. Before this discovery, only the five planets visible to the naked eye (Mercury, Venus, Mars, Jupiter, and Saturn) were known. Pluto was discovered much later (1930) and is now classified as a dwarf planet. Saturn was known to ancient civilizations long before the telescope was invented.