| Birth Date: | March 26, 1877 |
| Office1: | 25th Alabama State Treasurer |
| Governor1: | Benjamin M. Miller |
| Term Start1: | 1931 |
| Term End1: | 1935 |
| Predecessor1: | William Allgood |
| Successor1: | Charles McCall |
| Office2: | State Auditor of Alabama |
| Governor2: | Bibb Graves |
| Term Start2: | 1927 |
| Term End2: | 1931 |
| Predecessor2: | William B. Allgood |
| Successor2: | John M. Brandon |
| Office3: | 31st Secretary of State of Alabama |
| Governor3: | William W. Brandon |
| Term Start3: | 1923 |
| Term End3: | 1927 |
| Predecessor3: | William Peyton Cobb |
| Successor3: | John Marvin Brandon |
| Party: | Democratic |
Sidney Herbert Blan (March 26, 1877 – April 20, 1963) was a politician from Alabama. He served as Secretary of State of Alabama from 1923 to 1927, State Auditor of Alabama from 1927 to 1931, and Alabama State Treasurer from 1931 to 1935.
Before being elected for public office, Blan served as a Presidential Elector in the 1916 and 1920 Presidential Elections.
He married in 1901 and had two children. He died April 20, 1963.