Sergio Hierrezuelo Castellanos (born 15 March 1982) is a retired Cuban athlete who specialised in the 400 metres hurdles. He reached the semifinals of the 2005 World Championships. In addition, early in his career he won the silver medal at the 1999 World Youth Championships.
His personal best in the event is 49.11 seconds, set in 2005.
| Representing | ||||||
|---|---|---|---|---|---|---|
| 1999 | World Youth Championships | Bydgoszcz, Poland | bgcolor=silver | 2nd | 400 m hrd (84.0 cm) | 49.95 |
| 2002 | Ibero-American Championships | Guatemala City, Guatemala | bgcolor=gold | 1st | 400 m hurdles | 50.60 |
| 2003 | Central American and Caribbean Championships | St. George's, Grenada | bgcolor=silver | 2nd | 400 m hurdles | 50.26 |
| Pan American Games | Santo Domingo, Dom. Rep. | 6th | 400 m hurdles | 50.34 | ||
| 6th | relay | 3:06.27 | ||||
| 2005 | Central American and Caribbean Championships | Nassau, Bahamas | 4th | 400 m hurdles | 49.66 | |
| World Championships | Helsinki, Finland | 17th (sf) | 400 m hurdles | 49.66 | ||
| 2007 | Pan American Games | Rio de Janeiro, Brazil | 10th (h) | 400 m hurdles | 49.90 | |
| – | relay | DQ | ||||