Progress M-66 is a Soviet/Russian Progress cargo vehicle which docked to the ISS. It's the 122nd Progress flight.

Progress was the first cargo spacecraft to fly in space, and the first to bring freight back to Earth, thanks to a Raduga capsule.

It's a cargo ship developed to supply the Salyut 6 space station and which was subsequently used successively to supply the crews staying on board the Salyut 7, Mir and from the International Space Station. It made its first flight in 1978 and was the first vessel of this type: it enabled the crews to stay in space by bringing consumables (food, water, fuel, oxygen) and spare parts. In 2018, it was used with other cargo vessels to supply the permanent crew of the International Space Station.

The Progress spacecraft is largely derived from the Soyuz spacecraft intended for the transport of crews in low orbit. It is launched by a Soyuz rocket lifting off from the Baikonur cosmodrome. It has a mass of around 7 tonnes for a length of 7.9 meters and its carrying capacity is around 2.5 tonnes. It can transport both pressurized freight and gases, propellants and liquids but is not designed to bring freight back to Earth. Like the Soyuz spacecraft, it is equipped with a Kours automatic docking system. Several variants of the Progress spacecraft have been developed over the decades with increasing capabilities.