Police were alerted to the stabbing in Harehills Lane, Harehills, at about 15:40 GMT.
The wounded teenager was taken to hospital for treatment, but died a short time later.
A 15-year-old boy has been arrested on suspicion of murder, West Yorkshire Police said. He remains in custody for questioning.
Det Supt Pat Twiggs, of West Yorkshire Police, said: "This tragic incident happened in a busy area at a busy time of day with large numbers of people going about their daily business.
"I am appealing directly to anyone who witnessed the incident or has information that could help our inquiries to come forward."
The force is hoping to speak to anyone who saw a person running in the area or those who have mobile phone footage.
The scene remains cordoned off, with police forensic examinations expected to continue over the weekend.
A 16-year-old boy has died after he was stabbed in a busy Leeds street, prompting a murder inquiry.