Mamerto Alejandrino Natividad Jr. (December 3, 1871 – November 9, 1897) was a haciendero and a Filipino military leader who led numerous successful battles during the Philippine Revolution against the Spaniards.

Upon learning that Cabiao was among the rebel towns, the couple immediately packed their things and returned home to join the revolution, sending Mamerto's younger brother, Benito, ahead.

Three days later, his mother arrived, informing them that their father, Mamerto Natividad, Sr. had been executed by Spanish authorities on September 26, 1896, in San Isidro, together with attorney Marcos Ventus.

[1] On October 31, 1896, Mamerto was captured in Aliaga, brought to Manila and incarcerated in Bilibid after being mistaken for his father who had the same name but had already been executed.

[3] When he was freed, he and his brothers – Benito, Jose Salvador, Joaquin, Francisco and Pedro Manuel – joined the Philippine rebellion against the Spanish authorities to avenge their father's death.

In his book, Revolt of the Masses, Teodoro Agoncillo mentions that Gen. Mamerto Natividad, together with the eminent historian and poet, Jose Clemente Zulueta and Sr. Anastacio Francisco detested and convinced General Aguinaldo to reverse his pardon for the Bonifacio brothers.

"These men sang the same chorus, to wit, that the Bonifacio brothers must be liquidated in the interest of the Revolution since it had been made clear that Andres was intent upon having General Aguinaldo murdered and taking the highest position for himself.

He fought in the battles of Pintong Bato in Imus, Cavite (his brother Benito was wounded there), San Rafael and Baliwag, Bulacan.

We aspire to have a government which will represent all the active forces of the country, in which will take part the most capable, the most worthy in virtues and talents, without regard to their birth, their wealth, or the face to which they belong.

We desire that no friar shall set his foot on any part of the Archipelago, and that no convent or monastery or center of corruption, or partisans of that theocracy which has made this land another inquisitorial Spain, shall remain.

[3] Natividad's forces fought on for two more days, inflicting more casualties on the Spaniards, before retreating to the mountains with captured arms and ammunition.

On August 30, 1897, Gen. Mamerto Natividad came to the aid of the people of Santor, Bongabong, Nueva Ecija who had risen in arms against the Spaniards.

After three days of fighting, the Spanish forces had to surrender, even after receiving reinforcements from Zaragoza town under the commands of Generals Monet and Nuñez on Sept. 6, 1897.

For bravery, Natividad was elected chief commanding general of Central Luzon after the reorganization of the revolutionary government in Biak-na-Bato.

In his book, General Jose Alejandrino stated that "the major obstacle which Paterno encountered in his negotiations was the opposition of that unconquerable leader and he succeeded in his objective only after Natividad was dead.

With almost his last breath, he instructed his two brothers, Jose (Salvador) and Benito, to ask Don Emilio (Aguinaldo), in his name, for the release of Isidro Torres who was at the time under arrest.

"[6] General Torres was the commander of the "Apuy" guerillas and was incarcerated because he refused to sacrifice his men in a hopeless frontal attack against the enemy in a fortified position.

General Mamerto Natividad was carried by his comrades and his brothers in a hammock but he expired in Daang Kawayan on the way to Biak-Na-Bato at about 6 o'clock at dusk.

General Mamerto Natividad was buried with military honors in the bank of a river that flowed near Biak-na-Bato and a period of mourning was declared.

Aguinaldo declared that "Nobody may forget the 9th of November because on this day two great patriots lost their lives for the freedom of our mother country" referring to Natividad and Candido Tria Tirona.

Spanish authorities exiled the revolutionary leaders to Hong Kong, including Natividad's brother Benito and Jose Salvador.

Biak Na Bato, the headquarters established by Natividad for the Philippine Revolutionary Army was declared a national park in 1937 by President Manuel L. Quezon by virtue of its association with the history and site of the Biak-na-Bato Republic.