Portugal 2-1 Republic of Ireland
Cristiano Ronaldo broke a long-standing record with a late goal to rescue Portugal after he missed a penalty in the first half.
The hosts squandered a chance to go ahead from the penalty spot on 15 minutes when Ronaldo saw his spot-kick saved by Gavin Bazunu.
They were made to rue that miss as Ireland went on to take the lead on the stroke of halftime through John Egan's first international goal.
However, Ronaldo made up for his penalty miss in the second half as he rose well to head home a cross from Gancalo Guedes in the 86th minute.
With that goal, Ronaldo became the all-time leading scorer in men's international football with 110 goals.
Ronaldo was not done there as he snatched victory for the hosts with another trademark header in the sixth minute of time added on.
France 1-1 Bosnia-Herzegovina
Defending world champions France were unable to make a wining start after being held to a 1-1 draw by Bosnia-Herzegovina,
Edin Dzeko put the visitors ahead in the 36th minute, but the French weren't behind for too long thanks to Antoine Griezmann's strike in the 39th minute.
Norway 1-1 Netherlands
Louis van Gaal's return as Netherlands could not garner a win as his side drew 1-1 at Norway
Virgil van Dijk was back in the line-up after missing the European Championship as Louis van Gaal began his third stint in charge.
It was Erling Haaland who had the first say after giving Norway the lead on 20 minutes, but the Dutch got back on level terms through Davy Klaassen.
Russia 0-0 Croatia
Russia and 2018 World Cup finalists Croatia could not be separated at the Luzhniki Stadium after playing to a goalless draw.
Denmark 2-0 Scotland
Denmark made a solid start in Group F after defeating Scotland 2-0 at Parken on Wednesday evening.
The Danes broke the deadlock through Daniel Wass on 14 minutes while Joakim Mæhle doubled the advantage a minute later.
Check out the latest FIFA rankings!
