Q-Ship

"We are now in a flying donut, billions of miles from Earth."

- Iron Man

Q-Ships are massive spaceships used by Thanos and the Black Order. These ring-shaped vessels were stored inside the even larger Sanctuary II, and Thanos deployed them during his invasions of Zen-Whoberi and Earth.

Massacre of the Zehoberei
During Thanos' invasion of Zen-Whoberi, several Q-Ships patrolled the skies of the planet.

Attack on Greenwich Village
"I'm sorry. Earth is closed today. So pack it up and get out of here."

- Iron Man to Ebony Maw and Cull Obsidian In order to claim the Eye of Agamotto from Doctor Strange, two members of the Black Order, Cull Obsidian and Ebony Maw, flew to Earth in a Q-Ship, where they confronted the Master of the Mystic Arts and Iron Man. Finding himself to be unable to take the Eye from Strange, Maw beamed himself and an unconscious Strange to the Q-Ship, where Maw began torturing Strange for possession of the Eye.

Rescue of Doctor Strange
Iron Man and Spider-Man broke into the Q-Ship to rescue Doctor Strange and stop his captor, Ebony Maw, from retrieving the Time Stone. They killed Ebony Maw by ejecting him into space and stayed with Strange in the ship, which was traveling to Titan, so that they could defeat Thanos. Iron Man and Spider-Man crashed the vessel on Titan, where it was soon stormed by the Guardians of the Galaxy.

Trivia

 * The meaning behind the name "Q-Ship", first revealed by Entertainment Weekly, has not yet been clarified; the ship was never referred to by that name within Infinity War. However, the side view of the ship does visually resemble the letter "Q", suggesting that "Q-Ship" is a colloquialism for the vehicle.