After nine rounds, Le Quang Liem, Elo rating of 2713, was level with American rival Jeffery Xiong, Elo 2691, on 7.5 points.
They both competed for the championship title in a deciding game of blitz chess which Liem was able to win after 36 moves.
The victory represents the first time that the chess player from Ho Chi Minh City has been able to lift the World Open trophy and is the third championship he has won during the past month.
Both Quang Liem and Jeffery Xiong received prize money of US$15,000 for finishing level on 7.5 points, with the Vietnamese player earning an extra US$500 for winning via the tie-break.
The World Open 2019 chess tournament follows a Swiss one-round robin format and attracted 227 chess players, including 36 grandmasters, at this year’s event. Quang Liem was placed among the top seeds at No. 1.
Following the victory, Quang Liem has been invited to compete in the Grand Tour which will take place in Romania in November. He is one of three players to receive an invitation from organisers, including world No. 11 Vladislav Artemiev and Anton Korobov, who won an individual gold medal at the 43rd Chess Olympiad last year.
At the tournament in Romania they will face a number of famous players including Fabiano Caruana, Levon Aronian, Wesley So, Shakhriyar Mamedyarov, Sergey Karjakin, Anish Giri, and Viswanathan Anand in both rapid and blitz chess events.