Two-time Wimbledon winner Kvitova - a beaten finalist at the English seaside town tournament in 2011 - controlled a one-sided encounter from the outset on Saturday en route to triumphing 6-3 6-2 in just an hour and 16 minutes.
Eighth seed Ostapenko had previously not dropped a set all week at Devonshire Park but struggled to deal with the Czech's booming serve and blistering forehand during an error-strewn display.
Victory for Kvitova brought a 29th career singles title and a big confidence boost ahead of a first-round Wimbledon meeting with Italian Jasmine Pasolini.
Meanwhile, at Bad Homburg in Germany, Simona Halep was forced to withdraw from her semi-final against Bianca Andreescu on Friday due to a neck injury - just three days before the start of Wimbledon.
Unseeded Andreescu had a walkover to reach her sixth career final on Friday, and will meet Caroline Garcia in Saturday's final.
"I am sorry that I had to withdraw before my semi-final match," the former Wimbledon champ Halep said in a statement.
"But unfortunately I woke up this morning with a blocked neck and this is not allowing me to perform to the best of my ability."
Andreescu will contest her first final since the 2021 Miami Open nearly 17 months ago, where she was forced to retire against Ash Barty.
The 2019 US Open champion is playing her sixth tournament of the season following a six-month hiatus to look after her mental health.
Andreescu is bidding to win her fourth career title and will certainly be fresher than Garcia, who beat French compatriot Alize Cornet 7-6 (11-9) 3-6 7-5 in two hours and 45 minutes.
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