News that the deal had been done came courtesy of the club's official Twitter account:
According to Chris Bascombe of the Daily Telegraph, the transfer fee for the Brazilian youngster could reach a whopping £40 million.
The winger told Evertontv (via the club's official website) how excited he was to join:
"I want to have a lot of success with Everton. I think it is going to be important for me here to be with Marco Silva again. I will learn more because I am still learning as a player and I aim to develop and grow here.
"Everton have put their faith in me and I intend to honour this shirt and demonstrate on the pitch why I came here.
"I’ve known the manager for a while obviously, so I know how he works.
"I developed really well with him while he was with me at Watford. It was really good working with him and one day I believe he can help me to be selected for Brazil in the full national team.
"But that is for the future and my present is here with Everton. I want my dreams to become a reality here at one of the biggest clubs in England."
Phil Kirkbride of the Liverpool Echo outlined the reasons why Everton were so keen to get the Selecao youth international through the door:
The move sees Richarlison reunite with manager Marco Silva, who was in charge of Watford when the club landed the forward just a year ago. The 21-year-old played his best football of the 2017-18 season under the guidance of the Portuguese, helping the Hornets get off to a fine start.
However, Watford's and Richarlison's campaign stagnated when Everton approached the club about taking Silva to Goodison Park as a replacement for the sacked Ronald Koeman. While the Hornets eventually resisted the approach, a downturn in results saw Silva relieved of his duties in January.
As noted by Dale Johnson of ESPN, after taking the Premier League by storm early in the campaign, Richarlison's form nosedived:
When he did play well, Richarlison looked like one of the best young players in the top flight, as he seemingly had no issue adapting his game to English football following a move from Fluminense.
He provided pace, penetration and flair on the left flank, giving opposition full-backs a torrid time. He netted five goals and grabbed four assists before the turn of the year and appeared well-suited to the high-intensity football Silva is seeking to play.
Matt Cheetham of Sky Sports noted all the statistics point towards a footballer who will improve Everton:
Eyebrows will naturally be raised at the price tag, especially after Richarlison's form plummeted late in the campaign. The Toffees spent big money on a number of players last summer, and aside from the acquisition of Jordan Pickford, few of those deals really worked out; this is a gamble, with that in mind.
Still, Richarlison didn't have a summer break in 2017, is still young and made it clear he was unhappy to see Silva depart with a post on social media back in January.
There's no doubt the Brazilian has immense potential, and if harnessed correctly, he can become a wonderful player for the Toffees. Even so, given the reported fee paid for the player's services, there'll be a lot of pressure on Richarlison to shine on Merseyside.