The movie that usually gets credit for first putting computer-generated images on screen in a mainstream movie (in contrast with scientific and small experimental movies that tinkered with the technology very early) is Westworld in 1973.
To show the robot gunslinger’s point of view, they took regular filmed scenes and used computer processing to generate pixelated images, frame by frame. This is certainly computer-generated imagery, so it qualifies.
However, it is not computer modeled, which is what’s usually meant when someone refers to CGI. Star Wars generally gets the credit for that.
You can see the Westworld effect in this video.
