It was the 11th singles title for the 23-year-old Svitolina, who had won a tour-high five titles in 2017, and added Brisbane to that list earlier this year. The fourth-ranked Ukrainian improved to 14-2 for the year.
Svitolina was too strong for her Russian opponent in the 70-minute match, including an on-the-run, backhand cross-court shot in the fourth game and a forehand down the line in the seventh.
"I am very pleased with the performance throughout the week," Svitolina said. "When I had to play well, I played well. I did good at important moments. I was serving good, returning well, getting lots of balls back ... Maybe not amazing tennis, but I was pretty solid. It was enough."
"It feels amazing to have my name with them," Svitolina said. "It really motivated me."
Svitolina made the all-important break in the fifth game of the first set, and quickly asserted her dominance in the second by going 5-0 up with three breaks, the third coming at love. She then comfortably served out the match.
Coming into the match, Kasatkina had spent a total of 545 minutes on court -- against 297 for Svitolina, who also benefited from a first-round bye. But the Russian refused to blame tiredness for her lackluster performance in the final.
"It just happened. It's okay. If you are a top player, you are getting byes, and you are going through the first round. It is what it is," Kasatkina said. "It was tough. I think Elina, she was the toughest opponent for this final."
Despite the loss, the 20-year-old Kasatkina will move inside the top 20 when the rankings come out Monday.