The Argentine has dethroned Real Madrid rival Cristiano Ronaldo, who finished second, with Messi's teammates Luis Suarez and Neymar coming home third and fourth, respectively.
The 28-year-old attacker, who also claimed the trophy in 2009, 2011 and 2013, was rewarded for inspiring Barcelona to a historic treble triumph last season, as well as leading Argentina to the final of the Copa America.
Ronaldo, who was bidding for a fourth Goal 50 crown after becoming Real Madrid's all-time record goal scorer, finished second, just ahead of Messi's Barca teammates Luis Suarez and Neymar.
"I always say that, for me, the most important awards are collective ones, the ones that recognise us as the best at the end of the season," Messi told Goal.
"But I am also happy when I receive individual awards like this one. I am very grateful. Thank you."
Chelsea winger Eden Hazard came home fifth, with Bayern Munich duo Thomas Muller and Arturo Vidal ranking sixth and seventh, respectively.
Boca Juniors striker Carlos Tevez was eighth, just ahead of former Juventus teammate Paul Pogba, with Manchester City ace Kevin De Bruyne completing the top 10.
The Goal 50 rounds off a remarkable 12 months for Messi, whose return to his very best form at the turn of the year coincided with Barca's sensational charge towards the treble.
The Rosario native turned in one of the great individual displays in European Cup history in the first leg of his club's Champions League semifinal win over Bayern Munich and netted arguably the goal of 2015 with a sensational solo effort in the Copa del Rey final defeat of Athletic Bilbao.
The Goal 50 is an annual award that both recognises and ranks the world's 50 best footballers of the past 12 months.
Chief editors and correspondents from Goal's 37 editions around the world all cast their votes, with candidates judged on their level of consistency over the previous year of action, their big-game performances, footballing legacy and the success of their teams at both club and international level.