Cainta, officially the Municipality of Cainta (Filipino: Bayan ng Cainta, IPA: [kɐʔɪnˈtaʔ]), is a municipality in the province of Rizal, Philippines. According to the 2024 census, it has a population of 386,321 people.

It is one of the oldest municipalities in Luzon (founded on August 15, 1571) and has a land area of 4,299 hectares (10,620 acres).  It is also 3rd most populous municipality in the country after Taytay, Rizal and Rodriguez, Rizal. Its total assets amounting to ₱3,988,392,142.17 makes it the richest municipality in the country in terms of income.

Cainta was already a village named Cainta when the Spanish first arrived in the 1570s, recorded in Spanish records as Cáinta or Caynta. Its etymology is unknown.

After the death of Rajah Matanda, Adelantado Miguel de Legaspi received word that two ships, San Juan and Espiritu Santo, had just arrived in Panay Island in the central Philippines from Mexico. One ship was under the command of Don Diego de Legaspi, his nephew, and the other of Juan Chacon. The two ships were in such disrepair when they arrived in Panay that one of them was not allowed to return to Mexico. Legaspi ordered that it be docked on the river of Manila. The Maestro de Campo was sent to Panay to oversee its transfer to Manila, with Juan de la Torre as captain.

To help spread the faith, several Augustinian friars were commissioned by Spain and were among the ship's passengers. One of them was Father Alonso de Alvarado, who had been in the armada of Villalobos. Another was Father Agustin de Albuquerque, who became the first parish priest of Taal town, south of Manila. Some of the missionaries were sent to Cebu province in the central Philippines to accompany Father Martin de Rada the Prior. Four stayed to work in Pampanga province and the environs north and south of Manila, which included the then-village of Cainta.

Meanwhile, Legaspi was determined to subjugate the people of Cainta and Taytay, a neighboring town. He sent his nephew Juan de Salcedo with a galleon (a small ship propelled by oars and sails) and 16 small boats accompanied by a hundred Spanish soldiers and many Visayas natives allied with them. Salcedo sailed on August 15, 1571, arriving in Cainta on the 20th. He sought peace from the villagers but the village chiefs responded arrogantly, told him that the people of Cainta, unlike those of Manila, were not cowards, and would defend their village to the death. Confident in the defenses offered by their fort and the security of the site, they were joined by people from Taytay.

These two villages are on a plain on the shores of a river that flows from La Laguna and before arriving there divides in two large arms, both with abundant water. On its banks are found the two villages, half a league from each other, with the river passing through both before finally becoming one in a part of the terrain encircled by thick bamboo groves. These bamboos were tied together with liana, turning them into a thick wall where the people had constructed two ramparts with their moats full of water. By the river, they had built strong stone bulwarks with wooden towers and good artillery (culverins or lantakas), guarded by a large number of warriors armed with arrows, swords and other projectile-type arms.

Deciding to attack, Salcedo first sent Second Lieutenant Antonio de Carvajal with some escorts to reconnoiter the town and determine the weakest point where they could enter. Carvajal, wounded by an arrow in his arm, returned with the information that the weakest spot, the least fortified and with the easiest access was the other part of an arroyo on the side of La Laguna where many boats could be seen entering the river.