486958 Arrokoth (provisional designation 2014 MU₆₉; formerly nicknamed Ultima Thule) is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System visited by a spacecraft when the NASA space probe New Horizons conducted a flyby on 1 January 2019. Arrokoth is a contact binary 36 km (22 mi) long, composed of two planetesimals 21 and 15 km (13 and 9 mi) across, that are joined along their major axes. With an orbital period of about 298 years and a low orbital inclination and eccentricity, Arrokoth is classified as a cold classical Kuiper belt object.

Arrokoth was discovered on 26 June 2014 by astronomer Marc Buie and the New Horizons Search Team using the Hubble Space Telescope as part of a search for a Kuiper-belt object for New Horizons to target in its first extended mission; it was chosen over two other candidates, 2014 OS393 and 2014 PN70, to become the primary target of the mission.

When Arrokoth was first observed by the Hubble Space Telescope in 2014, it was designated 1110113Y in the context of the telescope's search for Kuiper belt objects, and was nicknamed "11" for short. Its existence as a potential target of the New Horizons probe was announced by NASA in October 2014 and it was unofficially designated as "Potential Target 1", or PT1. Its official provisional designation, 2014 MU₆₉, was assigned by the Minor Planet Center in March 2015, after sufficient orbital information had been gathered. The provisional designation indicates that Arrokoth was the 1745th minor planet to be assigned a provisional designation during the second half of June 2014. After further observations refining its orbit, it was given the permanent minor planet number 486958 on 12 March 2017.

Before the flyby on 1 January 2019, NASA invited suggestions from the public on a nickname to be used for the object. One of the choices, Ultima Thule, was selected on 13 March 2018. Thule (Ancient Greek: Θούλη, Thoúlē) is the northernmost location mentioned in ancient Greek and Roman literature and cartography, while in classical and medieval literature ultima Thule (Latin for 'farthermost Thule') acquired a metaphorical meaning of any distant place located beyond the "borders of the known world". Once it was determined that the body was a bilobate contact binary, the New Horizons team nicknamed the larger lobus "Ultima" and the smaller lobus "Thule". They are now formally named "Wenu" and "Weeyo", respectively.

Following the selection of the nickname, it was criticized by a Newsweek columnist because of the use of "Thule" by 19th-century racists as the mythical homeland of the Aryan race. The New York Times, crediting Newsweek, quoted several scientists and historians who expressed being unhappy about the name's connection to the Nazi Party. In November 2019, the International Astronomical Union (IAU) announced the object's permanent official name, Arrokoth.

The name Arrokoth was chosen by the New Horizons team to represent the Powhatan people indigenous to the Tidewater region of Virginia and Maryland in the eastern United States. The Hubble Space Telescope and the Johns Hopkins University Applied Physics Laboratory, which were prominently involved in Arrokoth's discovery, were both operated from the Tidewater region of Maryland.

With the permission of the elders of the Pamunkey Indian Tribe of the Powhatan nation, the name Arrokoth was proposed to the IAU and formally announced by the New Horizons team in a ceremony held at the NASA Headquarters in the District of Columbia on 12 November 2019. Prior to the ceremony, the name was accepted by the IAU's Minor Planet Center on 8 November, and the New Horizons team's naming citation was published in a Minor Planet Circular on 12 November.

The Powhatan language became extinct in the late 18th century and little was recorded of it. In an old word list, arrokoth is glossed as 'sky', and this was the meaning intended by the New Horizons team, but it would seem that it actually meant 'cloud'.