The hosts produced another impressive attacking display at Stadion Miejski, with Zuzanna Grzywińska scoring a hat-trick to take centre stage as Poland completed the group stage with three wins from three matches.
• Poland: Zuzanna Grzywińska 26', 63', 70', Kinga Wyrwas 31'
• Benin: Romaine Gandonou 87'
Poland made their dominance count in the 26th minute when Grzywińska reacted quickest to a loose ball following a corner to put the hosts ahead.
Five minutes later, Poland doubled their advantage. Kinga Wyrwas finished a flowing team move after Grzywińska's delivery from the right created the opportunity, giving Benin a difficult task before half-time.
Benin attempted to respond after the interval and forced Hanna Wieczerzak into important saves, with Romaine Gandonou and Yasminath Djibril among those testing the Polish goalkeeper.
But Poland soon regained control.
Grzywińska scored her second of the afternoon in the 63rd minute after following up on a powerful effort from Zuzanna Witek that struck the crossbar. Seven minutes later, the forward completed her hat-trick with a composed finish after an intelligent assist from Inez Sikora.
The result was already beyond doubt, but Benin refused to leave without something to show for their efforts.
In the 87th minute, Romaine Gandonou produced a superb free-kick to beat Wieczerzak and score Benin's consolation goal. It was a memorable moment for Gandonou in Benin's historic first appearance at the FIFA U-20 Women's World Cup.
Poland finished the match with 70 per cent possession, 21 shots and 11 attempts on target, underlining their control of the contest. Benin managed 14 shots, with four on target.
The victory gave Poland a perfect nine points from three matches, following earlier wins over Argentina and Mexico. They finished Group A with nine goals scored and only two conceded.
For Benin, the defeat ended their historic World Cup campaign. The debutants finished fourth in the group with one point from three matches, having previously drawn 2–2 with Mexico before suffering an 8–0 defeat to Argentina.
Grzywińska was named the Visa Player of the Match after her outstanding three-goal performance, while Poland now advance to the knockout stage with genuine hopes of making a deep run on home soil.