The 36-year-old scored twice in the final as Argentina saw off France to win the tournament for the first time in his illustrious career.
But it was his imperious form for his country in Qatar which saw him crowned Ballon d'Or winner by France Football once again.
Messi was presented with the award by David Beckham, owner of Inter Miami and runner-up in the 1999 Ballon d'Or.
"I couldn't imagine having the career that I've had," he said.
"Everything that I've achieved. The fortune I've had playing for the best team in the world, the best team in history. It's nice to win these individual trophies. To win the Copa America and then the World Cup, to get it done is amazing."
Kylian Mbappe - just the second man to score a World Cup final hat-trick - was third after starring in France's run to the final.
Kevin De Bruyne finished fourth while Rodri came fifth, Julian Alvarez - also a team-mate of Messi at international level - was seventh, and Bernardo Silva was ninth as City players dominated the top 10.
The 25-year-old won a league and Champions League double before playing a pivotal role in Spain's World Cup success, where she was also awarded the Golden Ball.
"This is a dream for me," she said.
"I have really good players by my side. To reach three straight Champions League finals as a club is special. Let's hope there's much more to come."
England international Jude Bellingham's meteoric rise continued as he was voted the Kopa Award winner for the best under-21 player in the world.
The Real Madrid and England midfielder picked up the trophy after finishing 18th for the main award.