Bournemouth have agreed a £30.6m (€35m) deal in principle with Vasco da Gama to sign winger Rayan after intense talks over the last 24 hours.
The 19-year-old's desire to join Bournemouth and play in the Premier League has been key to getting the deal done as the club negotiated his complex ownership structure.
The Brazilian teenager is seen as the long-term replacement for Antoine Semenyo, who joined Manchester City this month in a £64m deal.
But Rayan is a player the Cherries believe can have an impact immediately.
Rayan is a Brazilian youth international, having played at U17 and U20 level and has been on the radar of Brazil boss Carlo Ancelotti.
Rayan is expected to be in the UK later in the week to formally start his medical.