Wales beat Argentina 20-13 in Cardiff outscoring Pumas two tries to one.
Scrumhalf Williams crossed just after the break as the hosts claimed a first win in the fixture since 2018.
Wales head coach Wayne Pivac moved wing Louis Rees-Zammit [pictured below] to fullback after last Saturday’s heavy home loss to New Zealand.
The visitors, fresh from a win over England last weekend, were without captain Julian Montoya due to a rib injury with Pablo Matera stepping in as skipper.
The Pumas led 6-0 after a quarter of an hour as Emiliano Boffelli, their hero at Twickenham, kicked two penalties.
Pivac’s side reacted by camping in Argentina’s 22m but after successive carries hooker Ken Owens knocked the ball on centimetres from the Pumas line.
Six minutes after Owens’ mishap the home side led as No. 8 Taulupe Faletau bundled over from a rolling maul and Gareth Anscombe converted to make it 7-6.
Ospreys flyhalf Anscombe slotted a penalty to make it 10-6 at the break.
Their dominance continued after the break as Cardiff’s Williams blocked a Juan Cruz Mallia clearance kick to score and Anscombe added the extras as they led 17-6.
Just before the hour, Anscombe was replaced by Rhys Priestland before the 35-year-old extended his side’s advantage to 20-6 with a penalty.
Wales’ lead was cut to seven points as former Dragons prop Nahuel Tetaz Chaparro scored as Boffelli converted with 12 minutes to play.
Pivac’s side kept the Pumas pinned in their own 22m before holding on for victory in a welcome boost after last week’s humiliation against the All Blacks, especially with the Rugby World Cup less than 10 months away.
Wales 20 [Tries: Faletau, Williams; Cons: Anscombe 2; Pen: Anscombe, Priestland] Argentina 13 [Try: Tetaz Chaparro; Con: Boffelli; Pens: Boffelli 2]
Wales: 15 Louis Rees-Zammit, 14 Alex Cuthbert, 13 George North, 12 Nick Tompkins, 11 Rio Dyer, 10 Gareth Anscombe, 9 Tomos Williams, 8 Taulupe Faletau, 7 Justin Tipuric (captain), 6 Dan Lydiate, 5 Adam Beard, 4 Will Rowlands, 3 Dillon Lewis, 2 Ken Owens, 1 Gareth Thomas.
Replacements: 16 Ryan Elias, 17 Rhodri Jones, 18 Sam Wainwright, 19 Ben Carter, 20 Jac Morgan, 21 Kieran Hardy, 22 Rhys Priestland, 23 Owen Watkin.
Argentina: 15 Juan Cruz Mallia, 14 Mateo Carreras, 13 Matias Moroni, 12 Jeronimo de la Fuente, 11 Emiliano Boffelli, 10 Santiago Carreras, 9 Gonzalo Bertranou, 8 Pablo Matera (captain), 7 Marcos Kremer, 6 Juan Martin Gonzalez, 5 Tomas Lavanini, 4 Matias Alemanno, 3 Francisco Gomez Kodela, 2 Agustin Creevy, 1 Thomas Gallo.
Replacements: 16 Ignacio Ruiz, 17 Nahuel Tetaz Chaparro, 18 Eduardo Bello, 19 Lucas Paulos, 20 Facundo Isa, 21 Eliseo Morales, 22 Tomas Albornoz, 23 Matias Orlando.
Referee: Ben O’Keeffe (New Zealand)
Assistant referees: Angus Gardner (Australia) & Andrea Piardi (Italy)
TMO: Marius van der Westhuizen (South Africa)
