| Francisco Dueñas | |
| Order: | 6th and 11th |
| Office: | President of El Salvador |
| Term Start: | 26 October 1863 |
| Term End: | 15 April 1871 Provisional President until 1 February 1865 |
| Term Start1: | 1 February 1852 |
| Term End1: | 1 February 1854 |
| Predecessor1: | José María San Martín (provisional) |
| Successor1: | Vicente Gómez (provisional) |
| Term Start2: | 13 May 1851 |
| Term End2: | 30 January 1852 |
| Predecessor2: | José Félix Quirós (provisional) |
| Successor2: | José María San Martín (provisional) |
| Term Start3: | 12 January 1851 |
| Term End3: | 1 March 1851 Provisional President |
| Successor3: | José Félix Quirós (provisional) |
| Term Start4: | 1 February 1856 |
| Term End4: | 1 February 1858 |
| Term Start5: | 27 January 1855 |
| Term End5: | 24 February 1855 |
| Birth Name: | Francisco Dueñas Díaz |
| Birth Date: | 3 December 1810 |
| Death Place: | San Francisco, United States |
| Resting Place: | Santa Tecla, El Salvador |
| Nationality: | Salvadoran |
| Party: | Conservative |
| Children: | 3 |
| Profession: | Politician |
Francisco Dueñas Díaz (3 December 1810 – 4 March 1884) was a Salvadoran politician and member of the Conservative Party who served as President of El Salvador on four different occasions between 1851 and 1871. J. Lloyd Mecham described El Salvador during Dueñas' presidency as "experienced a far-reaching Conservative reaction".
Francisco Dueñas Díaz was born on 3 December 1810 in San Salvador, New Spain. His father was José Miguel Dueñas and his mother was Secundina Díaz. Dueñas attended the Santo Domingo Convent in San Salvador, studying to become a priest. In 1827, he transferred to the Order of Santo Domingo Convent in Guatemala City, however, he dropped out of the convent in 1829 and no longer sought the priesthood. In 1836, Dueñas earned his doctorate at the University of San Carlos in Guatemala City.
In 1837, Dueñas returned to El Salvador and was elected as a member of the Federal Congress of the Federal Republic of Central America as a conservative. The following year, he was elected as the secretary of the Federal Congress. In 1839, Salvadoran Governor Francisco Morazán appointed Dueñas as the vice secretary-general of dispatches. He served in this position until February 1840 when he resigned in protest of Morazán's invasion of Guatemala as a part of the Second Central American Civil War. In February 1845, Salvadoran President Joaquín Eufrasio Guzmán appointed Dueñas as the minister of dispatches, where he served until February 1846.
In 1849, Dueñas was elected to the Senate of El Salvador. In 1850, Dueñas attempted to run for president in that year's presidential election, but incumbent President Doroteo Vasconcelos did not allow Dueñas to do so as Vasconcelos was seeking re-election. From 12 January 1851 to 1 March 1851, Dueñas served as the provisional president of El Salvador as Vasconcelos led Salvadoran soldiers in the Battle of La Arada against Guatemalan President Rafael Carrera, after which, Dueñas ceded the provisional presidency to Vice President José Félix Quirós. On 13 May 1851, Quirós resigned the presidency and Dueñas assumed the presidency in an official capacity, serving the remainder of the 1850–1852 presidential term, resigning on 30 January 1852 to José María San Martín. Dueñas was elected as president during the 1852 presidential election and he assumed office on 1 February 1852, two days after he had resigned the presidency to San Martín. Dueñas served until 1 February 1854
On 27 January 1855, Dueñas was elected as the president of the Senate of El Salvador. He served until 24 February 1855. During the 1856 presidential election, Dueñas was elected as Rafael Campo's vice president. Dueñas served as vice president from 1 February 1856 to 1 February 1858. Dueñas supported Campo's presidency in opposition to liberal Gerardo Barrios who aspired to become the president of El Salvador; Dueñas saw Barrios as an enemy for his liberal politics. Dueñas fled El Salvador to Guatemala when Barrios overthrew President Miguel Santín del Castillo. He briefly returned to El Salvador for two months in 1861 after he was granted amnesty by Barrios, but Dueñas was forced to flee to Guatemala again after Barrios accused him of plotting to overthrow the government.
In 1863, Dueñas and other exiled conservatives supported Carrera's invasion of El Salvador and sought to overthrow Barrios. Barrios was overthrown on 26 October 1863 and Dueñas was proclaimed as El Salvador's provisional president. The legislature confirmed Dueñas' presidency during the 1864 presidential election and his term began on 1 February 1864. On 29 August 1865, the legislature amended article 33 of the constitution of El Salvador to allow Dueñas to run for re-election. He was successfully re-elected during the 1869 presidential election. Dueñas was overthrown by Field Marshal Santiago González Portillo on 15 April 1871 and seized the presidency.
Dueñas sought asylum in the United States embassy in San Salvador but he was eventually arrested and incarcerated at the military college established during Dueñas' presidency. In 1872, the Salvadoran government allowed Dueñas and his family to leave for exile in the United States. President Rafael Zaldívar accused Dueñas of attempting to overthrow his government in 1878 and 1883 when Dueñas attempted to reenter El Salvador on the boat named Ounalaska, and both times Dueñas was forced to return to the United States.
On 12 February 1866, Dueñas married Teresa Dárdano in a ceremony presided over by Tomás Pineda y Zaldaña, the bishop of San Salvador. Dueñas and Dárdano had three children: Francisco, Carlos, and Miguel. Dueñas also had two step children—Pablo and Antonia—through his wife's first marriage.
Dueñas died on 4 March 1884 in San Francisco, United States. His remains were returned to El Salvador in 1886 and he was buried in Santa Tecla.