The 21-year-old forward only moved to England in the summer of 2017, but quickly set about making his mark in the Premier League.
Richarlison is, however, to continue his career at Goodison Park under the guidance of former Hornets boss Marco Silva.
He told Everton’s official website of his ambition on Merseyside: “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.” Richarlison added: “I want to score more goals, provide more assists for my teammates and help in whichever way is possible.
“Everyone in the world knows Everton. It is a very big club, one of the biggest in England as I said. I am really happy and honoured to be here.”
Silva is delighted to have completed his first piece of business as Everton boss, with Richarlison a player he knows well and one he has brought the best out of in the recent past.
He said: “He is one more player who can help us. He is a good player who will make our team and our squad more competitive.
“The competition between our players is really important to me. This is what will make us better as a club, always that competition within the squad.
“The player himself is fast, strong, very good technically and he can play in three positions across the front line. He can also score goals.
“Evertonians will see a player who will be 100 per cent committed to helping our team always.”