The star with the largest known proper motion is Barnard's Star: 10.3 arc seconds per year.

In only 180 years, Barnard's Star moves a distance in Earth's sky equal to the width of the moon as we see it from Earth.

Barnard's Star is moving toward us at a speed of 165 kilometers (103 miles) per second. About 8,000 years from now it will become the closest star to ours. Barnard's Star will cruise past us, less than four light-years away and have a proper motion of 25 arc seconds per year!