Aiden McGeady made a goalscoring return as Celtic secured Scotland's first win in Europe this season at the final attempt.
The impressive McGeady, making his first start after more than five weeks out with knee trouble, fired home from 20 yards in first-half injury-time against 10-man Villarreal.
The Spaniards, who were already through to the last 16, had Guille Franco sent off after Shaun Maloney's headed opener.
