The Red Devils submitted a bid to RB Leipzig earlier this week, with Sesko preferring the move to Old Trafford rather than to Newcastle United, who were also keen on his services.
In an interview with the club's official website, the 22-year-old said: “The history of Manchester United is obviously very special but what really excites me is the future.
“When we discussed the project, it was clear that everything is in place for this team to continue to grow and compete for the biggest trophies again soon.
“From the moment that I arrived, I could feel the positive energy and family environment that the club has created. It is clearly the perfect place to reach my maximum level and fulfil all of my ambitions."
From Salzburg to Salford
It has been a successful career for Sesko to see him now in Manchester.
A 20-goal season at the age of 17 in Austria's second division caught the eye of parent club RB Salzburg, where he would spend his formative years.
It took him two of those to really break through into the first team and become a regular. Still a teenager, he would net his first goal in the Champions League, before moving over to Salzburg's sister club, Leipzig in the Bundesliga, for 24 million euros after the 2022/23 season.
Goals would continue to flow for the tall forward. In both his seasons in Germany, he has netted double-digit figures in the league, whilst contributing in cup competitions.
Now 22, he signs for Manchester United as they continue their search for a dominant number nine. He will compete with Rasmus Hojlund and Joshua Zirkzee for the starting berth, but it is likely he will make his debut against Arsenal next weekend.
'He can thrive'
Sesko has been linked with a number of clubs this summer, including the Gunners and Newcastle.
A deal with the Magpies was accepted by his former German club, but it was the player who opted to join Manchester United rather than head to the north east.
The director of football at Old Trafford, Jason Wilcox, said: “Benjamin possesses a rare combination of electrifying pace and the ability to physically dominate defenders, making him one of the most exceptional young talents in world football.
“We have followed Benjamin’s career closely; all of our data analysis and research concluded that he has the required qualities and personality to thrive at Manchester United."