| Valentín Alsina | |
| Nationality: | Argentine |
| Office: | National Senator |
| Term Start: | May 2, 1868 |
| Term End: | September 6, 1869 |
| Constituency: | Buenos Aires |
| Term Start1: | May 24, 1862 |
| Term End1: | April 30, 1868 |
| Constituency1: | Buenos Aires |
| Office2: | Provisional President of the Senate |
| Term Start2: | 1865 |
| Term End2: | 1869 |
| Predecessor2: | Pedro Ferré |
| Successor2: | Salustiano Zavalía |
| Term Start3: | 1862 |
| Term End3: | 1864 |
| Predecessor3: | Marcos Paz |
| Successor3: | Pedro Ferré |
| Office4: | Governor of Buenos Aires |
| Term Start4: | December 21, 1858 |
| Term End4: | October 23, 1859 |
| Predecessor4: | Pastor Obligado |
| Successor4: | Felipe Llavallol |
| Term Start5: | October 31, 1852 |
| Term End5: | December 7, 1852 |
| Predecessor5: | Manuel Guillermo Pinto |
| Successor5: | Manuel Guillermo Pinto |
| Birth Date: | December 16, 1802 |
| Birth Place: | Buenos Aires, Viceroyalty of the Rio de la Plata |
| Death Date: | September 6, 1869 (aged 66) |
| Death Place: | Buenos Aires, Argentina |
| Spouse: | Antonia Maza de Alsina |
| Profession: | Lawyer |
| Party: | Unitarian Party |
Valentín Alsina (December 16, 1802 – September 6, 1869) was an Argentine lawyer and politician.
Alsina was born in Buenos Aires and studied law at the University of Córdoba. He occupied diverse posts in government, and had a successful civil career as an advocate and professor of law at the University of Buenos Aires.
Under the government of Juan Manuel de Rosas, he had to leave the country, as his liberal ideas did not please the dictator at all. From his refuge in Montevideo, he supported the opposition against de Rosas, both financially and through publications.
When Rosas was deposed by Justo José de Urquiza, Alsina returned to Buenos Aires, and he was elected provincial Governor in 1852. However, he resigned after a few months, shortly before a military coup took place. In 1853, Buenos Aires left the Argentine Confederation and declared itself an independent state. Alsina, a fervent supporter of Buenos Aires Province independence, became Governor again in 1857. In 1859, open hostilities broke out between Buenos Aires and the Argentine Confederation, led by Urquiza. After the defeat of the Buenos Aires army at the Battle of Cepeda on October 23, 1859, Alsina had to resign his post, and shortly after Buenos Aires rejoined the Confederation. Alsina became a member of the Argentine Senate in 1862.
When Bartolomé Mitre (President of Argentina between 1862 and 1868) offered him a position as member of the Argentine Supreme Court he refused and remained serving as a Senator until his death, which occurred just a few months after he took the oath of his son Adolfo Alsina, who became Vice President of Argentina in 1868.