Williams helps Tigers turn the tables
The Irish province had inflicted a record 38-0 defeat on Leicester in Round Three, but the wounded Tigers came out fighting to earn their second victory in this season's competition.
Munster looked to have snatched a second successive victory when Tyler Bleyendaal converted Niall Scannell's drive over score to make it 16-15 with three minutes remaining.
But flyhalf Williams rose to the occasion to send a penalty through the uprights from 52 metres out to claim a revenge triumph.
Glasgow Warriors are now out in-front in Pool Four after four rounds of Champions Cup action.
It was end-to-end stuff in the opening exchanges at Welford Road, but Munster made the most of their first opportunity to get points on the scoreboard.
Simon Zebo chipped ahead but was taken out by George Worth and Bleyendaal made no mistake with the long-range kick.
Bleyendaal added a second penalty to make it 6-0, before Manu Tuilagi opened the door for Munster when he was shown yellow for a shoulder charge on Rory Scannell.
But instead, it was the 14-men of the Tigers who roared back into the game.
Ellis Genge and Luke Hamilton combined to take Leicester deep into Munster territory, before Peter O'Mahony gave a penalty away in-front of the posts.
And Owen Williams made no mistake from the tee to cut the gap to 6-3.
The Welshman added a second penalty moments later to level the scores at 6-all at half-time.
It was more of the same after the interval as both sides fought to gain the ascendancy.
Much like the first-half, it was Munster who hit the front with a Bleyendaal penalty after Brendan O'Connor went off his feet at a ruck.
But Williams levelled once again with his third penalty, before Leicester snatched the lead for the first time.
Munster infringed again at a ruck and Williams made no mistake to make it 12-3 with 25 minutes remaining.
Munster looked to be building up a head of steam 10 minutes later, but the ball went loose and Adam Thompstone went on the attack. Zebo dragged him down moments after he had put boot-to-ball, and earned a yellow card. Williams landed the resulting penalty to earn a vital six-point lead.
But Munster were not dead and buried. Scannell crashed over at the back of a maul, before Bleyendaal converted, despite a slip, to put the Irish province 16-15 ahead.
But Williams showed nerves of steel to land the long-range penalty in the dying moments.
The scorers:
For Leicester:
Pens:Williams 6
For Munster:
Try:Scannell
Con: Bleyendaal
Pens: Bleyendaal 3
Yellow cards: Manu Tuilagi (Leicester Tigers, 29), Simon Zebo (Munster, 65), Tom Youngs (Leicester Tigers, 74)
Teams:
Leicester Tigers: 15 George Worth, 14 Peter Betham, 13 Jack Roberts, 12 Manu Tuilagi, 11 Adam Thompstone 10 Owen Williams, 9 Ben Youngs, 8 Lachlan McCaffrey, 7 Brendon O’Connor, 6 Luke Hamilton, 5 Graham Kitchener, 4 Ed Slater, 3 Pat Cilliers, 2 Tom Youngs (captain), 1 Ellis Genge.
Replacements: 16 Harry Thacker, 17 Logovi'i Mulipola, 18 Greg Bateman, 19 Mike Fitzgerald, 20 Mike Williams, 21 Will Evans, 22 Sam Harrison, 23 Tom Brady.
Munster: 15 Simon Zebo, 14 Darren Sweetnam, 13 Jaco Taute, 12 Rory Scannell, 11 Keith Earls, 10 Tyler Bleyendaal, 9 Conor Murray, 8 CJ Stander, 7 Tommy O’Donnell, 6 Peter O’Mahony (captain), 5 Billy Holland, 4 Donnacha Ryan, 3 John Ryan, 2 Niall Scannell, 1 Dave Kilcoyne.
Replacements: 16 Rhys Marshall, 17 James Cronin, 18 Stephen Archer, 19 Jean Kleyn, 20 Jack O’Donoghue, 21 Duncan Williams, 22 Ian Keatley, 23 Andrew Conway.
Referee: Pascal Gauzere (France)
Assistant referees: Maxime Chalon (France), Jean-Luc Rebollal (France)
TMO: Eric Gauzins (France)
Source: @ChampionsCup