The Barcelona striker capitalised on an error by Saudi Arabia midfielder Abdelulelah Al Malki before sending a composed finish past onrushing goalkeeper Mohammed Al Owais.
Lewandowski was visibly emotional after ending a run of four World Cup games without finding the net.
Piotr Zielinski had given Poland a first-half lead from Lewandowski’s cutback, but Saudi Arabia were awarded a penalty five minutes later for Krystian Bielik’s foul on Saleh Al Shehri.
Wojciech Szczesny kept out Feras Al Brikan’s effort before producing a sensational one-handed stop to prevent Mohammed Al Burayk from burying the rebound.
Saud Abdulhamid was denied by Sczcesny and Al Brikan shot over the bar in the second half, while Arkadiusz Milik and Lewandowski were both denied by the woodwork as Poland sought to double their lead on the counter-attack.
Lewandowski’s late strike ended Saudi Arabia’s hopes of building on Tuesday’s remarkable victory over Argentina and boosts Poland’s hopes of reaching the last 16 for the first time since 1986, when they were beaten 4-0 by Brazil in the first knockout round.
Czeslaw Michniewicz’s team play Argentina in their final Group C game on Wednesday, while Saudi Arabia face Mexico at the same time.
Source – BBC