Common for an informal group or club organized around a shared interest, especially at universities or within companies. Often translated as 'club' rather than literally as 'circle'.
I joined a film club at university.
I run on weekends with the company's running club.
circle; circular shape
Used for a circle as a visual or graphic shape. In everyday geometry or ordinary description, 円 or 丸 may be more native-sounding.
There is a blue circle in the center of the logo.
I joined a tennis club at university.
I started a photography club with some friends.
I got busy and quit the club.
circle lens; circle contact lens