While Lukaku took the headlines, Nemanja Matic also enjoyed an assured home debut following his £40 million switch from Chelsea.
Romelu Lukaku introduced himself to Old Trafford in triumphant fashion with two goals as Manchester United crushed West Ham United 4-0 in an impressive Premier League opener on Sunday.
The Belgium striker, a £75 million ($97.6 million, 82.5 million euros) signing from Everton, struck either side of half-time to take his tally of goals against West Ham to 11 in his last 11 appearances.
Substitute Anthony Martial and Paul Pogba added late goals that gave a true reflection of United's dominance and sent Jose Mourinho's side to the top of the early-season standings on goal difference.
United join Arsenal, Manchester City and Tottenham Hotspur on maximum points and while West Ham offered scant resistance, the early signs suggest Mourinho's men will not end the season 24 points off the pace again.
While Lukaku took the headlines, Nemanja Matic also enjoyed an assured home debut following his £40 million switch from Chelsea and there were strong showings from Pogba, Henrikh Mkhitaryan and Marcus Rashford as well.
West Ham manager Slaven Bilic, who gave league debuts to Joe Hart, Pablo Zabaleta, Marko Arnautovic and Javier Hernandez, will hope for better when his side visit Southampton next weekend.
Having opened his account in Tuesday's UEFA Super Cup loss to Real Madrid in Macedonia, Lukaku now has three goals in two United games.
He might have been able to celebrate his first league goal even sooner.
Mkhitaryan's pass freed Juan Mata and when the Spaniard's shot was blocked by West Ham goalkeeper Hart, he squared the ball to Lukaku, but the 24-year-old could not get a shot away.
Mata's darting runs into the box were bringing United joy and he almost broke the deadlock when he raced onto Pogba's clever dinked pass and slipped a shot past Hart, only for Angelo Ogbonna to hack clear.
United's pressure told in the 33rd minute thanks to a move started and finished by home debutants.
Matic had already seduced the home fans with his awareness and coolness on the ball and he sprang a United counter-attack by racing out to block an attempted pass by Pedro Obiang.
Picking up the loose ball, Rashford tore into the West Ham half and slid a pass into the box for Lukaku, whose first-time shot clanged off the left-hand post and nestled in the side-netting on the other side of the goal.
While United old boy Hernandez endured a thankless first half on his return to Old Trafford, Andre Ayew threatened an equaliser in stoppage time with a rasping drive that David de Gea had to parry.
Lukaku picked up where he had left off in the second half, first releasing Rashford to run through and shoot wide and then doubling his tally in the 52nd minute.
Former Manchester City stalwart Zabaleta's foul on Rashford gave United a free-kick on the left and from Mkhitaryan's cross, Lukaku stole between Winston Reid and Arthur Masuaku to plant a header past Hart.
Arnautovic served a reminder of West Ham's threat with a header that De Gea was obliged to tip over, but it seemed only to redouble the home side's determination to stretch their lead.
After Rashford had left the right-hand upright shuddering with a curler from the left-hand apex of the area, Mkhitaryan released Martial to coolly tuck away United's third before Pogba swept in the fourth from 20 yards.