The 32-year-old Colombian midfielder joins from Fiorentina, having also played for Aston Villa in the past.
Sanchez becomes another in a busy window for the Hammers, in which they have broken their transfer record twice this summer.
Issa Diop arrived for more than £24million in June, before that fee was beaten for the signing of Felipe Anderson for £45m.
But, it has become as much about the bargains as it has about the big spending, with Jack Wilshere and Ryan Fredericks joining on free transfers.
While the likes of Lucas Perez, Lukasz Fabianski and Andriy Yarmolenko have also arrived, Sanchez could take the place vacated by Cheikhou Kouyate, who joined Crystal Palace early in the summer.
Sanchez joins having previously suffered relegation with Aston Villa, having joined them in 2014.
Following their drop to the Championship, the Colombian midfielder signed for Serie A outfit Fiorentina on a loan deal, before making it permanent 12 months later.
But he struggled for game time and was subsequently sent out to Espanyol until end of the season in January.
He will expect to face competition for places from the likes of Wilshere, Mark Noble, and Pedro Obiang, among others.
Source: Read Full Article