The EuroLeague Best Defender is an annual basketball award of the European premier level EuroLeague. It is awarded to the best defensive player throughout the season, up until the EuroLeague Final Four stage of the season. The award began in the 2004–05 season, and the winner is selected by the EuroLeague's head coaches. Dimitris Diamantidis of Panathinaikos Athens, won the first five awards, from 2005 to 2009.

Dimitrios 'Dimitris' Diamantidis is a retired Greek professional basketball player, who spent the last twelve seasons of his EuroLeague career with Panathinaikos. Widely regarded as one of the greatest European players ever to grace the game, he marked his era by being the most versatile player in the EuroLeague, serving as an inspiration to a whole generation of young European stars. Diamantidis is the only Greek player who is a member of both the EuroLeague 2000–10 All-Decade Team and the EuroLeague 2010–20 All-Decade Team.