Riyad Mahrez's double and Jamie Vardy's opener earned the Foxes an easy 4-2 win over the wretched Black Cats.
England striker Vardy's header and Mahrez's brace, one coming from the penalty spot, put Leicester in complete control after just 25 minutes.
Jermain Defoe pulled one back but Marc Albrighton ended the contest with the Foxes' fourth, even though Steven Fletcher made it 4-2.
The win gave Ranieri, who replaced Nigel Pearson in the summer, his first win in charge in his first Premier League game in 11 years.
The Italian gave Shinji Okazaki his Foxes bow but fellow new-boys Christian Fuchs, Yohan Benalouane and N'Golo Kante were on the bench while Jeremain Lens and Younes Kaboul started for the Black Cats.
However, it was one of the stars of last season who fired Leicester into a 12th minute lead.
Ranieri had challenged Vardy to score more goals after he netted five last season - earning an England call - and the forward responded instantly when he flicked Albrighton's free-kick across goal and the Black Cats allowed it to bounce in off the woodwork
It came after Kasper Schmeichel, a spectator for most of the half, denied Defoe from point-blank range after the striker wriggled free in the sixth minute.
But that was the only fear for the Foxes as they took total control inside half an hour.
Mahrez saw a shot deflect wide off Kaboul but eventually doubled Leicester's lead on 18 minutes when he powered in a 12-yard header from Albrighton's cross.
And seven minutes later he made it 3-0 when, after being brought down in the area by Lee Cattermole, the Algerian international sent Costel Pantilimon the wrong way from the spot.
Dick Advocaat responded by replacing Cattermole with Fletcher but it failed to give the visitors any foothold in a game which was already lost.
And Danny Drinkwater almost added a fourth from distance when his effort was palmed away a minute before half time.
There was little Leicester let-up and Mahrez continued to torture Sunderland after the break as he turned them inside out before hitting the post 10 minutes after the restart.
Pantilimon then saved from Vardy and Mahrez as Leicester threatened to embarrass the visitors.
But they pulled a goal back against the run of play on 60 minutes when Adam Johnson slipped Defoe in to fire into the corner from 10 yards.
Suddenly Defoe was alive and Schmeichel was forced into a smart low save two minutes later with Leicester rattled.
Albrighton made it 4-1 with 25 minutes left
The visitors failed to clear Mahrez's cross and, when Vardy's presence caused problems, the ball fell to Albrighton to drill in from the edge of the area
The goal rush continued five minutes later, though, when Fletcher made it 4-2, heading into an empty net after Defoe lobbed Schmeichel.
It kept the Foxes on their toes and Okazaki was denied a debut goal by Kaboul's block with four minutes left.
TWEET OF THE MATCH
"Just nipped outside at half-time to see that #SAFC have kept the engine running."
BBC commentator Connor McNamara posts a picture of the Sunderland team coach.
https://twitter.com/ConorMcNamaraIE/status/630029617215184896
PLAYER RATINGS
Leicester:
Kasper Schmeichel: 7 (Out of 10)
Ritchie De Laet: 7
Wes Morgan: 7
Robert Huth: 7
Jeff Schlupp: 7
Mark Albrighton: 8
Danny Drinkwater: 7
Andy King: 7
Riyad Mahrez: 9
Shinji Okazaki: 7
Jamie Vardy: 8
Subs:
Yohan Benalouane: 6
Christian Fuchs: 6
N'Golo Kante: 6
Sunderland
Costel Pantilimon: 7
Billy Jones: 5
Sebastian Coates: 5
Younes Kaboul: 5
Patrick Van Aanholt: 5
Jack Rodwell: 5
Lee Cattermole: 4
Sebastian Larsson: 5
Jeremain Lens: 5
Jermain Defoe: 6
Adam Johnson: 5
Subs:
Steven Fletcher : 6
Adam Matthews: 6
STAR PLAYER
Riyad Mahrez: The Algeria international ran Sunderland ragged all afternoon and deserved a hat-trick
His first-half brace put Leicester in complete control and he was only denied the match ball by the woodwork and fine saves from Costel Pantilimon
The Foxes need to prove they can maintain their form from last season and Mahrez, one of their stars from their Great Escape, will be key
MOMENT OF THE MATCH
Kasper Schmeichel: Had little to do all game but he laid the foundations for Leicester's win with a vital sixth-minute save
Jermain Defoe had wriggled free in the area only to be denied by the keeper from point black range with the score still 0-0
Six minutes later and the Foxes' rout began but only after Schmeichel had given them a platform
VIEW FROM THE BENCH
Dick Advocaat is third favourite to be the first Barclays Premier League manager to be sacked this season and his odds will not have improved after seeing his side's first-half collapse
Opposite number Claudio Ranieri could not have wished for a better start at Leicester after replacing Nigel Pearson this summer
The Italian needs to impress to silence the doubters after his surprise appointment and certainly got off to the best start
MOAN OF THE MATCH
Claudio Ranieri will be delighted with a debut victory in charge of Leicester but is sure to be annoyed at conceding twice to a Sunderland side who were beaten inside the opening 25 minutes
There seemed little danger to the Foxes' backline but Jermain Defoe and Steven Fletcher pounced when the hosts switched off in the second half
It will only be a mild concern but Ranieri will want perfection from his new side
NEXT UP
West Ham v Leicester (Premier League, Saturday August 15)
Sunderland v Norwich (Premier League, Saturday August 15)
Source : PA
Source: PA