| Honorific-Prefix: | The Honourable |
| Alejo Mabanag | |
| Office: | 30th Secretary of Justice |
| Appointer: | Carlos P. Garcia |
| Term Start: | July 14, 1959 |
| Term End: | December 30, 1961 |
| Predecessor: | Enrique Fernandez |
| Successor: | José W. Diokno |
| Office1: | Senator of the Philippines |
| Term Start1: | December 30, 1953 |
| Term End1: | December 30, 1959 |
| Constituency1: | At-large |
| Term Start2: | May 25, 1946 |
| Term End2: | December 30, 1949 |
| Constituency2: | At-large |
| Term Start3: | 1931 |
| Term End3: | 1935 |
| Predecessor3: | Alejandro de Guzmán |
| Successor3: | Post abolished |
| Constituency3: | 2nd district |
| Term Start4: | 1922 |
| Term End4: | 1928 |
| Predecessor4: | Pedro María Sison |
| Successor4: | Teofilo Sison |
| Constituency4: | 2nd district |
| Office5: | Member of the Lingayen Municipal Council |
| Term Start5: | 1916 |
| Term End5: | 1919 |
| Birth Date: | 14 July 1886 |
| Birth Place: | San Fernando, La Union, Captaincy General of the Philippines |
| Party: | Nacionalista |
| Alma Mater: | University of Santo Tomas (BA) La Jurisprudencia (LLB) |
Alejo Razulo Mabanag (July 14, 1886 – ?) was a Filipino lawyer and politician.
Mabanag was born on San Fernando, La Union, to Liberato Mabanag of Camalaniugan, Cagayan and Manuela Razulo of Bangar, La Union.[1]
Mabanag worked as a clerk in the Executive Bureau from 1903 to 1912. During that time, he finished his Bachelor of Arts degree at the University of Santo Tomas in 1908 and his Bachelor of Laws degree from La Jurisprudencia in 1912.[1] He then placed second in the bar examinations the same year and opened a law firm in Lingayen, Pangasinan.
Mabanag was elected to the Lingayen municipal council from 1916 to 1919. He successfully ran for Senator to represent the Second Senatorial District from 1922 to 1928 and from 1931 to the abolition of the Senate in 1935.[1]
Upon the establishment of the Commonwealth government in 1935, President Manuel L. Quezon appointed him Judge of the Court of First Instance of Iloilo up to 1938 and later named as city fiscal of Manila until 1945.[1]
He successfully ran for an at-large seat in the Senate in 1946 but lost reelection in 1949. Nevertheless, he stayed in the chamber as chief counsel of the Senate Blue Ribbon Committee and in the 1953 elections was elected again as a Senator under the Nacionalista Party ticket.[1]
In 1959, he was appointed by President Carlos P. Garcia to become his Secretary of Justice before his term in the Senate ended. He served until 1961.[2]
He was married to Jacoba Ramirez[3] and had 13 children.