The victory gave him his second career ranking title, his first coming in the 2015 Indian Open.
Murphy had beaten Jamie Jones 4-3 in his semi-final, and White scored a 4-1 victory over Mitchell Mann.
The 26-year-old Welshman won the title with a 97 break in the final frame.
Craigie stuns Un-Nooh in Scottish Open qualifying
Murphy beat Jamie Jones in the semi-final 4-3, while White defeated Mitchell Mann 4-1 in order to set up the clash.
Hendry thumped by Taylor in Scottish Open qualifying
Northern Ireland Open
Northern Ireland Open 2021 - Draw, schedule, results and all you need to know