The community answers are split between Minolta A mount and Sigma SA mount, so the safest conclusion is that it needs closer inspection before you can identify it with confidence.

A good first step is to check the rear lens cap or the lens barrel for mount markings such as “for Minolta,” “for Sony/Alpha,” or “SA.” Older Sigma lenses were made in several mounts, and the same lens model may exist in different versions.

If it is Minolta A mount, it will fit Minolta AF cameras and later Sony Alpha A-mount bodies. If it is Sigma SA mount, it is for Sigma SA-mount cameras only.

To confirm, compare the rear mount shape and the electronic contacts to reference photos for both mounts. Since it does not fit Nikon or Canon, that is not unusual—many Sigma lenses were made specifically for other systems.

In short: it is most likely either Minolta A or Sigma SA, and the definitive way to tell is by the mount markings or a visual comparison of the rear bayonet.