I think you'll find it was...
Certainly the first with 3d graphics.
However, I'm happy to be proved wrong if you can show an earlier example.
Hi Siobhan,
The very first space trader was actually a text only game called Star Trader which came out in 1974 and was written in BASIC (for the Atari I think). There was also a multiplayer 3D space combat game in the same year called Spasim (yes you read that right...multiplayer...in 1974) which ran on the PLATO computer system