Metroid Prime 2: Echoes is a 2004 action-adventure game developed by Retro Studios and published by Nintendo for the GameCube. The sequel to Metroid Prime (2002), Echoes is the sixth main installment in the Metroid franchise. It was released in North America, Europe and Australia in 2004. In Japan, it was released in May 2005 as Metroid Prime 2: Dark Echoes.

The story follows bounty hunter Samus Aran after she is sent to rescue Galactic Federation Marines from a ship near Aether, a planet inhabited by a race known as the Luminoth. She discovers that the troops were slaughtered by the Ing, a hostile race that came from an alternate dimension of Aether. Samus must travel to four temples to ensure the destruction of the evil Ing, while battling them, wild creatures, Space Pirates, and her mysterious doppelgänger, Dark Samus.

Retro sought to differentiate Echoes with a heavier focus on storytelling, new gameplay mechanics, and a multiplayer feature. Nintendo launched a viral marketing campaign that included several websites written as if taking place in the Metroid universe. The single-player mode was acclaimed for its graphics, atmosphere and music, though its steep difficulty and multiplayer mode were criticized.

Echoes received several awards and spots on "top games" lists by Nintendo Power and IGN. More than 1.10 million copies were sold worldwide. Metroid Prime 3: Corruption was released in 2007. In 2009, an enhanced version of Echoes was released for Wii in Japan and as part of Metroid Prime: Trilogy.