The host nation had been touted as favourites ahead of the inaugural Finals and they lived up to that billing in Porto, adding more major silverware to their European Championship triumph three years ago.
Cristiano Ronaldo had netted a hat-trick in the 3-1 semi-final win over Switzerland but he was kept relatively quiet on this occasion by Virgil van Dijk and Matthijs de Ligt.
Instead it was left to Guedes to settle matters, exchanging passes with Bernardo Silva and smashing home from the edge of the box, although Jasper Cillessen may feel he could have done better.
Cillessen, winning his 50th cap, was the busier goalkeeper in the opening half-hour, although he was only called upon to make a trio of routine saves – twice from Bruno Fernandes long-range efforts either side of gathering Jose Fonte's header.
Fernandes remained a threat, curling narrowly over from the edge of the box as the hosts continued to look likeliest to score as the interval approached.
Netherlands were sharper after the break and Rui Patricio got down smartly to thwart Georginio Wijnaldum, but on the hour Portugal had the goal their play deserved.
Guedes found Silva, who returned the ball with a nicely disguised pass, and the Valencia man rifled into the bottom-right corner via the left hand of Cillessen.
Patricio saved impressively from Memphis Depay's header as Netherlands sought a swift response but the closest they came was Marten de Roon firing over from 20 yards as Portugal held on to lift another major international trophy.
What does it mean? More success for Santos
Portugal's Euro 2016 success was built upon the foundation of a solid defensive base, but their Nations League semi-final win over Switzerland was a thoroughly entertaining affair and Fernando Santos' side were a far superior attacking force against Netherlands.
Ronaldo picks his battles
Portugal's talisman started off in a central role but, as the game wore on, he could be seen drifting out to the left with greater frequency. Perhaps frustrated by being so well shackled by De Ligt and Van Dijk, the Juventus star left a hole that Silva and Guedes surged into for the winner.
UEFA Nations League (@UEFAEURO) June 9, 2019
Oranje lacking penetration
In Van Dijk and De Ligt, Netherlands have a centre-back pairing that is the envy of world football. But their starting front three of Ryan Babel, Steven Bergwijn and Depay were largely ineffective on this occasion. Ronald Koeman will be praying his forwards can match the standards set by his imperious backline.
Key Opta Facts
- Portugal have won two of the last four competitive international tournaments they have appeared in, with their previous triumph coming at Euro 2016.
- Portugal are the first European nation to host and win a final of a major competition since France beat Brazil 3-0 in the final of the 1998 World Cup.
- Netherlands have lost four of their last five finals in major international tournaments (three in the World Cup, once in the Nations League).
- Netherlands remain winless against Portugal when playing them in Portugal, drawing two and losing four of their six such meetings.
- Goncalo Guedes has been directly involved in five goals in his last eight appearances for Portugal (three goals and two assists).