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In a rain-disrupted final, Fritz produced an impressive performance on serve to maintain his dominant recent record against Zverev. The American fired 11 aces, did not face a break point and won 88 per cent of his first-serve points to improve to 8-5 against the German.

Fritz, who has won his past five meetings against Zverev, will return to number-four in the ATP Rankings with the win. The American displaces British lefty Jack Draper, who had dislodged Fritz in fourth spot a week earlier.

"It was not so great a clay season, so to come here and start the grass season off perfectly, I am super happy to get the title and to do it here," Fritz said.

Fritz did not drop a set all week at the ATP 250 event in Germany and is the first player to lift a tour-level trophy without losing serve since Giovanni Mpetshi Perricard in Basel last October.

Among active players, only Novak Djokovic has more grass-court titles (8) than Taylor Fritz. The American has claimed four, including three at Eastbourne, putting him level alongside Matteo Berrettini and Nicolas Mahut.

Fritz arrived in Stuttgart seeking form, having suffered a shock opening-round exit against Daniel Altmaier at Roland Garros. The second seed looked comfortable all week in Germany and was in control for large periods against Zverev.

The American rushed the German with his depth and aggressive forehand in the opening set, clinching the decisive break in the eighth game before holding serve to lead. Rain suspended play for 65 minutes at the start of the second set and when the players returned, there was little between the Top 10 stars. With a tie-break left to decide the set, Fritz fired three winners and benefited from Zverev errors to capture his first title of the season.

Zverev was seeking his 25th tour-level crown but first on grass, having lost finals in Halle in 2016 and 2017.