Malolos [maˈlɔlɔs], officially the City of Malolos (Filipino: Lungsod ng Malolos), is a component city and capital of the province of Bulacan, Philippines. According to the 2024 census, it has a population of 269,809 people. It is the capital city of the province of Bulacan as the seat of the provincial government.

Malolos was the site of the constitutional convention of 1898, known as the Malolos Convention, that led to the establishment of the First Philippine Republic led by Emilio Aguinaldo, at the sanctuary of the Barasoain Church. The convent of the Malolos Cathedral served as the presidential palace at that time. The First Philippine Republic is sometimes characterized as the first proper constitutional republic in Asia, although there were several Asian republics predating it – for example, the Mahajanapadas of ancient India, the Lanfang Republic, the Republic of Formosa, or the Republic of Ezo. Aguinaldo himself had led a number of governments prior to Malolos, like those established at Tejeros and Biak-na-Bato which both styled themselves República de Filipinas ("Republic of the Philippines"). Unlike the founding documents of those governments, however, the Malolos Constitution was duly approved by a partially elected congress and called for a true representative democracy.

Miguel Lopez de Legazpi conquered the 8 villages along Malolos River and integrated it into one entity dated November 14, 1571, and constituted it as an Encomienda de Malolos the Adelantado entrusted the settlements to conquistador Don Marcos de Herrera. On April 5, 1572, Legazpi merges the encomiendas of Malolos and Calumpit into a single entity to form a new town of Calumpit with Juan Moron and Herrera as co-encomenderos.

On April 15, 1572, Legazpi entrusted 6 villages along Atlag River and given it to Don Jeronimo Tirado.

Nine years later, Malolos was officially established as a town and included it in Bulacan and dismembered on Alcaldia de Calumpit on June 11, 1580, and accepted as priory with Fray Matheo de Mendoza as its first minister in an Augustinian Council held in Tondo Convent but the civil administration still belongs to its encomendero at that time, Don Jeronimo Tirado.

The Tagalog constituted the majority of the Malolos populace although it is said that the town had a Kapampangan origin; the name Malolos is a Spanish pronunciation of Kapampangan word maluslús. They were led by prominent families, among them are descendants of the royal clans of Gatbontons, Gatmaitan, Gatsalian (Gatchalian), Dimagiba, Lakandola, Ladia and Lacancale and in the 17th-19th centuries, Chinese Filipino families through Tondo and Binondo, such as Chichioco, Cojuangco, Chiong, Chico, Cunanan, Tantocos, Tanchangco, Tanjosoy, Tengco, Tenjeco, Tiongson, Lomotan, Manahan, joined by Spanish Filipino families of Adriano, Bautista, Jacinto, Reyes, Santos, Rustia, de Leon, Agustin, Vasquez, Valenzuela, Crisostomo and Estrella.

Chinese Filipino traders settled in Malolos starting in 1670 for economic opportunity. The settlers increased, and Malolos began engaging with textile, rice production. However, the Chinese are expelled from the town on June 30, 1755, due to political and social issues.

On August 31, 1859, Malolos was divided into three independent towns; "Malolos", "Barasoain, and "Santa Isabel". These new towns are former districts of Malolos, with own respective Presidente Municipal and Parish priests. With the beginning of American rule in 1903, these towns were again reunited into a single municipality. The two other districts became barangays under the political jurisdiction of Malolos.