Mariano Marcos y Rubio (Spanish pronunciation: [maˈɾjano ˈmaɾkos i ˈruβjo]; April 21, 1897 – March 8, 1945) was a lawyer, educator, and politician from Batac, Ilocos Norte, Philippines. A Congressman from 1925 to 1931, he is best known for being the father of Ferdinand Marcos, who was the president of the Philippines from 1965 to 1986, and the grandfather of the current president Bongbong Marcos.

There are conflicting accounts about the exact nature of his death, with the mainstream version coming from American guerrilla unit leader Major Robert Lapham saying that he was drawn and quartered in Bacnotan, La Union by Lapham's guerrilla unit for being a Japanese collaborator. The guerrilla unit was led by Kumander Tasyo (Anastacio Badua Buccat of Galongen, Bacnotan, La Union). This was corroborated by Luis Buccat Aquino, a nephew of Kumander Tasyo, and a member of the guerrilla unit. The Marcos family maintains he was executed by the Japanese, despite Marcos's known collaboration with the imperial government during the war.

He is the namesake of two Philippine state universities: the Mariano Marcos State University in Ilocos Norte, and the Don Mariano Marcos Memorial State University in La Union, as well as the town of Marcos, Ilocos Norte.^{[citation needed]}

Mariano Marcos was born in Batac, Ilocos Norte on April 21, 1897, to Fabián Marcos y Galimba and Cresencia Rubio y Manglal-lan. A farmer, the elder Marcos had served as gobernadorcillo and justice of the peace of Batac after the Philippine Revolution, who championed the Ilocano language but at the same time cultivated a scholarship in the Spanish language.

A militant follower of Gregorio Aglipay and member of the Philippine Independent Church, he had his son baptised and raised in the Aglipayan faith. Mariano Marcos had his primary and intermediate education in his hometown. Then he went to Manila to study at the Philippine Normal School (now the Philippine Normal University), where he graduated in 1916.

Right after he received his diploma, the Bureau of Education named him maestro insular in Laoag, a position he held until 1917, when he was promoted to maestro principal. A year later, he was enlisted in the National Guard and given the rank of lieutenant. On September 16, 1919, after passing a rigid examination, he was named supervising teacher, a position that required traveling and doing the rounds of the public schools in the whole province. He held this position until January 4, 1921, when he resigned to accept the position of high school teacher at the National University. There is no record whatsoever that Mariano Marcos ever graduated with a law degree from the University of the Philippines. Nor could he have been the class valedictorian in the University of the Philippines College of Law, since the class valedictorian was Rafael Dinglasan. He and his lawyer-brother Pio opened a law office in Batac, with a branch in Manila.

Meanwhile, with the encouragement of his friends and admirers, he had entered politics. Running under the banner of the Nacionalista Party, and backed by the majority of his fellow Batacqueños, he was elected representative of the second district of Ilocos Norte. Marcos was considered one of the most effective speakers in the entire province during his time. His powerful voice gave him an edge over other politicians during political rallies. He successfully ran for the same position in 1928. In the legislature, he obtained the chairmanship of the powerful committee on ways and means, and likewise served as member of other committees including those on public instruction, public works, public estate, and mines and natural resources. He bid for the same seat in 1932, but lost to his rival from Laoag, Emilio Medina, a consequence of the Batac vote being divided between him and his town mate and fellow candidate, Julio Nalundasan.

In 1935, Marcos cast another bid at the legislature, this time for a seat at the National Assembly under the Commonwealth government, but lost to Nalundasan. Two days after the elections, Julio Nalundasan was hit in the head by a rifle shot while inside his home and died instantly. Mariano Marcos, his son Ferdinand, his brother Pio, and his brother-in-law Quirino Lizardo, were accused of the crime and eventually arrested and tried for the crime in 1938. He and his brother were eventually acquitted but his son and brother-in-law were both convicted. A Supreme Court decision penned by Associate Justice Jose P. Laurel would reverse the conviction in 1940. It is believed that the young Marcos's godfather Ferdinand Chua who was also the municipal court judge in Batac interceded for him.