List of largest optical telescopes in the 18th century

List of largest optical telescopes in the 18th century, are listings of what were, for the time period of the 18th century, large optical telescopes. The list includes various refractor and reflector that were active some time between about 1699 to 1801. It is oriented towards astronomy, not terrestrial telescopes (e.g. spyglass).

A James Short's reflecting telescope;this English telescope maker produced almost 1400 Gregorian reflectors in the mid-1700s. Mobile versions were used to observe the Transit of Venus.

Many of the largest were metal mirror reflectors, some of which had substational apertures even for the 20th century. One problems was that many instrument makers including Herschel did not pass on their mirror making craft, and by the next century reflectors had largely been passed over in favour of small achromats (2 lens refractors). It was not until the 21st century that really large refactors would predominate once again. Some of the achievements in astronomy of the 19th century telescopes include the discovery of the planet Uranus, the Messier catalog, and overall increased detections of comets, stars, star catalogs, and other charting.

The major breakthrough in the 1700s, was the discovery of two and even three lens telescopes and increased spread of reflecting telescopes and their designs. In this period reflectors used metal mirrors not metal coated class, which was not pioneered until the next century.