Russian boxing star Sergey "The Krusher" Kovalev loves him some Vladimir Putin and he's not ashamed of it ... telling TMZ Sports he thinks Putin is the greatest Russian prez EVER.
We got Kovalev out in L.A. and asked him his thoughts on Putin ... who's a pretty polarizing figure these days, with some saying he's a great leader, and others saying he's a threat.
Kovalev definitely is the former ... telling our guy not only does he think Putin is a "good" president, but the best president Russia has ever had.
R.I.P. Boris Yeltsin.