Gallacher had six birdies in the 12 holes before his eagles in the third round and is at 21-under 195 after 54 holes. That is a tournament record.
Richard Sterne, who had led after each of the first two rounds, had a 6-under 66 but it wasn't enough to keep pace with Gallacher. Sterne has a 54-hole total of 18-under.
Thorbjorn Olesen, with a 67 Saturday, sits in third at 16-under and three players are at 14-under.
Sterne opened his third round with a bogey but was 7-under the rest of the way. He was 3-under on both the pars 3s and par 5s Saturday.
Gallacher started the day one stroke back of Sterne but could have easily been in the lead as he had back-to-back bogeys in both the first and second rounds. He went bogey-free Saturday, however, and is three clear as he looks for his first European Tour title since October 2004.
He had three birdies in his first five holes Saturday and closed the first nine with another. After back-to-back birdies at 11 and 12, Gallacher needed just an 8-iron to reach the pin on the 550-yard 13th. His shot hit the flag and stopped 4 feet away for a short eagle putt.
His second shot at the 564-yard 18th found a bunker but he dropped in the 40-yard shot for his second eagle of the day and fourth of the tournament.