| Club: | Chelsea |
| Season: | 1909–10 |
| Manager: | David Calderhead |
| Chairman: | Claude Kirby |
| Owner: | Gus Mears |
| Stadium: | Stamford Bridge |
| League: | First Division |
| League Result: | 19th |
| Cup1: | FA Cup |
| Cup1 Result: | Second round |
| League Topscorer: | Jimmy Windridge (6) |
| Season Topscorer: | Jimmy Windridge (6) |
| Largest Win: | 4–1 v Bristol City 4–1 v The Wednesday |
| Largest Loss: | 1–5 v Liverpool |
| Highest Attendance: | |
| Lowest Attendance: | |
| Pattern B1: | _chelsea1905h |
| Pattern So1: | _2bluestripes |
| Leftarm1: | 96C5A2 |
| Body1: | FFFFFF |
| Rightarm1: | 96C5A2 |
| Shorts1: | FFFFFF |
| Socks1: | 000000 |
| Pattern So2: | _2bluestripes |
| Leftarm2: | 8B0000 |
| Body2: | 8B0000 |
| Rightarm2: | 8B0000 |
| Shorts2: | FFFFFF |
| Socks2: | 000000 |
| Prevseason: | 1908–09 |
| Nextseason: | 1910–11 |
The 1909–10 season was Chelsea Football Club's fifth competitive season and fifth year in existence. They club finished 19th in the First Division and were relegated.