The 23-year-old, seeded fourth, fired a total of 29 aces on his way to his second title of the year following his victory in Budapest in April. He also reached the final in Marseille earlier this year.
The 35-year-old Lopez, who last reached a final in August 2016, was aiming for a sixth career title and third on grass when he broke early in the first set to race into the lead.
He then had a handful of opportunities to break again with the score at 1-1 and 2-2 in the second but Pouille held serve and eventually claimed the set on a tiebreak.
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Pouille's patience paid off when a double fault and two unforced errors from Lopez gave the Frenchman his first break points midway through the third set. He took his chance at the first opportunity and then comfortably held serve.
Pouille who saved a matchpoint against Jan-Lennard Struff in the round of 16, squandered his first against Lopez with a double fault but made amends on his third with an ace.
(Reporting by Karolos Grohmann; Editing by Toby Davis)
