He surpasses the record of Colombia keeper Faryd Mondragon, who was 43 years and 3 days old in his final appearance at the 2014 World Cup.
Al Muwallad took the spot-kick, but his firm strike was brilliantly pushed onto the bar by the veteran.
That's because Egypt goalkeeper Essam El-Hadary became the oldes player to play in a World Cup at the age of 45.
Salem Al-Dawsari sealed the win for Saudi Arabia in added time of the second half.
It was Egypt's first goal from open play at a World Cup since 1934 and Salah, who converted a penalty against Russian Federation in their second group game, should have doubled the advantage minutes later.
Not bad for the oldest player in World Cup history...
Egypt ended their World Cup campaign without a single point in three games, as they struggled to match the quality of their group rivals.
Italy asks Malta to seize migrant ship
The U.N.'s refugee agency says around 80,000 people are expected to arrive by sea this year, about half the number from 2017. Malta responded that it would "act according to the laws and applicable conventions", without further explanation.
Senegal, Japan: underdogs aiming for a round of 16 spot
In their final group games on Thursday, Senegal will face Colombia in Samara while Japan plays Poland in Volgograd. Panama , one of the weakest teams in the field from the ultra-weak CONCACAF region is just happy to have qualified.
Cannabis legalization in Canada officially law as bill receives royal assent
Federal and provincial consumption taxes will also apply - varying between 10 to 15 per cent depending on the province. It was said most of past year that legal sales would pop off in the beginning of July 2018 - right around Canada Day.
It has been a busy World Cup for both referees and their VAR helpers, who between them have set a new benchmark at the worldwide celebration of football.
Saudi Arabia played their best match of the tournament, showing quality football virtually throughout the entire 90 minutes.
It was Egypt who broke the deadlock on 21 minutes as Salah latched onto a long ball before lobbing the on-rushing Yasser Al Mosailem to nestle the ball in the back of the net.
Egypt's tournament has been a fairytale turned horror story with the injury saga of their key player Mohamed Salah.
"We got to the final of the African Nations Cup playing in this way".
It was an opening half of record achievements and firsts.
El Hadary produced a stunning save to deny Al Muwallad, but his celebrations were cut short when a second penalty was awarded for Gabr's tug on Al Muwallad's shirt. That changed in the 41st minute when the Asian side were awarded a penalty for Ahmed Fathy's handball.