The judge said Derek Chauvin's sentence was based "on your abuse of a position of trust and authority, and also the particular cruelty shown" to Mr Floyd.
Mr Floyd, 48, died after Chauvin knelt on his neck for nine minutes.
His murder caused global protests against racism and police brutality.
Chauvin, 45, was convicted of second-degree murder and other charges last month. During his trial, his lawyer described the killing as "an error made in good faith".
Chauvin was also told to register as a predatory offender and was barred from owning firearms for life.
