Issa Diop will undergo a medical at West Ham ahead of a £21.9m move from French club Toulouse, according to Sky sources.
The France U21 centre-back has been a prime target for the Hammers this summer and is close to completing his move to the London Stadium.
Diop is due in London on Monday for a medical exam and to finalise personal terms after a deal was agreed with the French Ligue 1 club last week.
Monaco, Marseille, RB Leipzig and Sevilla have all been interested in signing the promising young defender.
He made 31 appearances as Toulouse narrowly avoided relegation last season, taking his tally to just under 100 for the club.
Toulouse-born Diop has represented France at every youth level from U16 to U21, for whom he has five caps.