Yes, the game that started it all in 1994, System Shock, is now available on Steam and GOG.

It's an Enhanced Edition (which also includes the classic version of the game), containing several of the community's mods and improvements on the original game and much more, such as mouselook support, remappable keys, or enhanced resolution.

So go ahead, Employee 2-4601, grab a copy and jump back into Citadel Station!