France’s Monfils, who was appearing in a fourth final at the competition, needed just 61 minutes to secure his seventh ATP World Tour title.
Having been granted a walkover in the semifinals by Dominic Thiem‘s illness, Monfils showed all the benefit of his extra rest as he produced some of his most dogged tennis to outgun Rublev.
“I’m very happy,” said Monfils afterwards. “I like this tournament so much. I always come back, and I finally got it. So I’m just very happy and very proud.
“It’s been a while. I was waiting for that moment to get back in shape. In 2016, I was almost on my top and I had a very good year, finishing at No. 6.
“I couldn’t really defend my chances in 2017. I had a long rest and came back strong in 2018, which was a goal. I wouldn’t say I was expecting to win the first tournament, but I’m more than happy that I did.”