Allan Barcellos Silveira (born 27 July 1992), is a Brazilian football coach.
Graduated in physical education from PUC-RS, Barcellos began his career as a coach in the youth categories of Grêmio, where he worked from 2013 to 2021.
Barcellos arrived at São Paulo in 2022, to command the under-13 team. He progressed through the club's youth sides, before being appointed head coach of the under-20 squad on 24 May 2024. He stood out for the great reaction obtained in the Campeonato Brasileiro Sub-20, and also won the Copa do Brasil Sub-20 in December of that year.
In January 2025, Barcellos led the under-20s of Tricolor to the main youth category title in Brazilian football, the Copa São Paulo de Futebol Júnior. He reached the finals for the second consecutive year, again losing the trophy, before asking to leave the club in March 2026, after not being able to move to the first team.