The former Real Madrid, Liverpool and Bayern Munich player took over Leverkusen in the relegation places in October and took them to a sixth-place finish, alongside a run to the Europa League semi-finals. 

Alonso's performance at Leverkusen led to speculation he may be tempted away from the club to one of Europe's bigger sides, but the new deal will keep him at the BayArena for the next three seasons. 

The Spaniard thanked the club for "the trust Bayer have in me" and said there is "a great deal of closeness and understanding between those responsible for the club and me".

"I see last season positively. But I want more, just like the club," he continued. 

"We are continuing to work on this with determination."

Sporting Director Simon Rolfes said the extension is "an expression of great appreciation and mutual trust" between the club and manager. 

Leverkusen have already signed former Arsenal captain Granit Xhaka this summer, but lost winger Moussa Diaby to Aston Villa.