| Alejandro Manuel Sinibaldi Castro | |
| Office: | Acting President of Guatemala |
| Term Start: | April 2, 1885 |
| Term End: | April 6, 1885 |
| Predecessor: | Justo Rufino Barrios |
| Successor: | Manuel Barillas Bercian |
| Office2: | First designated to the Presidency of Guatemala |
| President2: | General Justo Rufino Barrios |
| Birth Date: | 1825 |
| Death Date: | 1896 |
| Nickname: | Flor de un día[1] |
| Children: | Cristina, María del Carmen, Concepción, Carlos and María Sinibaldi y Ramírez |
| Parents: | Alejandro de Sinibaldi y Albora, and Máxima Castro Gálvez |
| Spouse: | Carmen Ramírez |
Alejandro Manuel Sinibaldi Castro (1825 - 1896) was acting President of Guatemala from April 2, 1885, to April 5, 1885.
Of partial Italian descent, Sinibaldi Castro was a businessman who was "First Designate to the Presidency", the equivalent of Vice-President, during the presidency of Justo Rufino Barrios.
When Barrios was killed on April 2, 1885, in El Salvador, Sinibaldi Castro became acting president. However, given that Sinibaldi Castro had no political connections and was not in the military, he was pressured to resign within days of taking over.
His successor was General Manuel Lisandro Barillas, who served as acting president, and was eventually elected as Constitutional President.
. Federico Hernández de León. El libro de las efemérides. Tipografía Nacional. Guatemala. Tomo III. 1930.