Johan Slager (8 June 1946 – 22 January 2025) was a Dutch musician best known as the original guitarist of rock band Kayak.

Slager co-founded the band along with Ton Scherpenzeel, Pim Koopman, and Max Werner in 1972.

During and after his time with Kayak, Slager played with many Dutch artists; he played on albums by Circus Custers, Bolland & Bolland and Ekseption, and formed his own band called Plus Doreen.

His guitar sounds can also be heard on albums by his ex-Kayak mates Max Werner and Edward Reekers.

Together with befriended musicians they played in Dutch pubs, doing mostly covers (Rolling Stones, Bob Dylan, The Band, etc.).