The England midfielder was in excellent form once again at the London Stadium, notching the eighth and ninth goals respectively of his prolific loan stint from Manchester United in the first half as David Moyes’ side leapfrogged Liverpool and Chelsea back into fourth spot in the Premier League, just one point behind the Foxes.
Jarrod Bowen coolly finished West Ham’s third just after the interval, with the hosts belying the absences of injured key duo Declan Rice and Michail Antonio to produce a vital win in the crowded battle for a top-four finish.
However, they once again came close to frittering away a 3-0 lead, with Arthur Masuaku’s error allowing Kelechi Iheanacho to rifle home a lifeline for Leicester with 20 minutes remaining.
Iheanacho struck again in the early stages of six minutes of second-half stoppage time to tee up a grandstand finish, with West Ham just about holding on as Wesley Fofana headed a great chance wide with the last touch of the game.
Lingard’s first goal was unorthodox but featured real quality as he drove Vladimir Coufal’s smart cut back into the ground on the half-volley but somehow still managed to bend it around the defender and into the bottom corner.
The second was more straightforward, with Bowen setting up Lingard for a simple finish into an empty net after Issa Diop’s long ball had beaten the Leicester defence.
FA Cup semi-finalists Leicester were well below par and fell further behind shortly after the break, with Bowen coolly slotting beyond Kasper Schmeichel after a clever pass from Tomas Soucek.
West Ham thought they had a fourth goal when a quick free-kick caught Leicester cold and Lingard’s ball to the back post was headed in off the woodwork by Diop, but the VAR correctly ruled it out for offside.
Leicester suddenly sparked into life and got a gift when Masuaku’s rogue pass went straight to Iheanacho, who took one touch before rifling beyond Lukasz Fabianski.
Only some committed challenges from Fabianski and captain Mark Noble - whose 400th Premier League appearance was ended early by an arm injury - then kept the Foxes at bay, with everything going through substitute Marc Albrighton down the right flank.
Iheanacho caused panic in the West Ham ranks in stoppage time, prodding home after Albrighton’s cross had deflected off Diop.
Fofana had a super chance to level in the final moments, but could only head wide of the post - much to Moyes’ relief.