The following is a list of Halley-type comets (HTCs), which are periodic comet with an orbital period between 20 and 200 years, often appearing only once or twice within one's lifetime. The majority come from between the orbits of Saturn and Neptune; Due to the nature of their orbits, their orbits can be perturbed by the giant planets and sent into orbits too far from the Sun to outgas, and vice versa. Minor planets in comet-like orbits similar to HTCs that never come close enough to the Sun to outgas are called Centaurs. HTCs are named after the first discovered member, and the first discovered periodic comet, Halley's Comet, which orbits the Sun in about 75 years, and passing as far as the orbit of Neptune.
This list contains only Halley-type comets which are not numbered yet because they have been observed only once. To find Halley-type comets observed several times, see the list of numbered comets and sort them by orbital period to filter those with 20 years or more.