Cygnus NG-15 (Northrop Grumman-15) is a cargo resupply mission of the Northrop Grumman Cygnus spacecraft to the International Space Station under the Commercial Resupply Services contract with NASA.

Northrop Grumman and NASA jointly developed a new space transportation system to provide commercial cargo resupply services to the International Space Station. The Cygnus cargo ship consists of two parts, a service module built in the USA based on the GEOStar platform, and a pressurized module, manufactured in France and Italy by Thales Alenia. The cargo is sent into orbit by a launcher specially developed for this purpose.

Antares has a first stage based on Energiya lateral blocks, made in Ukraine by Yuzhnoye. It was initially powered by two NK-33s, built in the 1960s for the Soviet N1 lunar launcher, before being replaced by RD-181s, derived from the RD-170s installed on Energiya and Zenit. The second stage, a Castor-30, is made in the USA, by Northrop Grumman.

CRS NG-15 was captured by RMS on 22/02/2021 at 09:38 UTC and berthed to the Nadir port of the Unity module of the International Space Station on 22/02/2021 at 12:16 UTC. Its stay on the ISS was 127 days. It was unberthed on 29/06/2021 at 13:20 UTC and released by RMS on 29/06/2021 at 16:32 UTC. It deorbited on 02/07/2021 at 01:30 UTC.