Emersonn has signed a five-year contract at Portman Road after beating fellow promoted side Hull City to his signature. He scored six goals in 28 Ligue 1 appearances for Toulouse last season, having joined the French club from Turkish side Goztepe a year earlier, and has represented Brazil at youth level.
"I am very proud to sign for Ipswich Town," Emersonn said. "Playing in the Premier League is something I have always dreamed of and I know I have picked the perfect club to do that with. I will give everything for the team every time I play and I can't wait to get started and meet my new team-mates as well as the supporters."
Chairman Mark Ashton described the deal as "an exciting moment for the club".
He said: "As we prepare for our return to the Premier League we know recruitment will be crucial, with the club investing significantly in this area in recent years in order to bring the best possible talent from across the globe to the club.
"In making Emersonn our first signing of the summer we know we have acquired a young, hungry player with a high ceiling, with more signings to follow as we continue to invest to give ourselves the best possible chance of achieving our goal in the Premier League."
Manager Gary O'Neil said there had been "plenty of interest" in the striker before Ipswich won the race for his signature.
Ipswich have also tied down winger Wes Burns to a new one-year contract, keeping the Wales international for a sixth season. Burns has made 164 appearances since joining from Fleetwood Town in 2021, scoring 30 goals and playing a part in three promotions, though injury restricted him to 18 appearances last season.
"I am so proud to have represented Ipswich Town for the last five years and to have achieved so much during that time," Burns said. "Winning a third promotion last season was really special for the club and the town and also for me personally, after working so hard to get back on the pitch after a long time out through injury. I'm really motivated to compete at the highest level again and help the club take the next step."
O'Neil said Burns' experience would be valuable as Ipswich prepare for their second crack at the Premier League.