Police were called to London Road just after 6.30pm yesterday to reports of a fight amongst a group of people.
Nobody was found when police arrived, but just after 7, a teenager went to hospital with stab wounds, but died soon afterwards.
A stop and search order is in place in areas across Croydon until just after 10.30 this morning.
Anyone with information is asked to contact police, or Crimestoppers to remain anonymous.