She had stunned sixth seed Kristina Mladenovic in the opening round and defeated last year's runner-up Alize Cornet in the quarter-finals before battling past Anastasija Sevastova in the last four.
She will move up to No.4 for this month's Australian Open, where she will have a target on her back as she attempts to go beyond the third round for the first time.
World No.88 Sasnovich of Belarus - ranked 72 spots lower than her opponent - called for a medical timeout after the first set to have new strapping applied to quell a leg complaint that has troubled her throughout the tournament.
In doing so, the Belarussian became the only qualifier ever to reach the tournament's final.
WTA Auckland Classic: Semifinals: Julia Goerges bt Hsieh Su-Wei 6-1, 6-4; Caroline Wozniacki bt Sachia Vickery 6-4, 6-4. World number six Svitolina enjoyed a breakthrough season in 2017 - winning five tournaments, including three Premier 5 events.
Svitolina beat Belarusian qualifier Aliaksandra Sasnovich 6-2, 6-1 in a lopsided night final to win her 10th title on the women's elite tour.
In each set Svitolina made two breaks and held on to his service never made a problem situation. The returner won just five points in the opening five games before Sevastova built a 15-40 lead in the sixth game, only to see Sasnovich fight off the first break point with an acute volley victor and the second courtesy of another error from the Latvian.
Goerges, who lost to American Sloane Stephens in the 2016 Auckland final, was far more comfortable in both of her matches.
Trailing early in the contest, Svitolina reeled off seven of the next eight games to take the first set.
Having not left Queensland Tennis Centre until after midnight following her impressive semi-final victory over No. 2 seed and defending champion Karolina Pliskova on Friday evening, Svitolina said she had to disguise her fatigue in the final. In personal meetings the Ukrainian was leading with the score 2:0.