Cars was the first Pixar Cars film to show Lightning McQueen's racing number as 95.
Lightning's number 95 appears on his body and racing decals throughout the original 2006 film. The number became one of the character's most recognizable visual identifiers and remained associated with him in later films and merchandise.
The number is a reference to 1995, the year Pixar released Toy Story, its first feature-length film. This connection is an in-universe design detail with a studio-history meaning, linking Lightning's identity to Pixar's own beginnings.
Cars 2 and Cars 3 also feature Lightning racing with number 95, so the question asks which film introduced it rather than which film contains it. Cars on the Road, a later Disney+ series, likewise uses established Cars characters and visual details but did not originate Lightning's number.