The information comes just hours after Chelsea, under interim coach Calum McFarlane, lost the FA Cup final to Manchester City 1-0.
According to transfer journalist David Ornstein, the former midfielder has agreed to a four-year deal to coach Chelsea.
The last permanent head coach at Chelsea was Liam Rosenior, who was fired earlier this year after just 23 games at the helm.
Alonso has previously coached Real Madrid and Bayer Leverkusen.
