Third District, formerly Poblacion, is a barangay in the municipality of Jalajala, in the province of Rizal. Its population as determined by the 2015 Census was 3,091. This represented 9.58% of the total population of Jalajala.

According to the 2015 Census, the age group with the highest population in Third District is 20 to 24, with 335 individuals. Conversely, the age group with the lowest population is 75 to 79, with 17 individuals.

Combining age groups together, those aged 14 and below, consisting of the the young dependent population which include infants/babies, children and young adolescents/teenagers, make up an aggregate of 30.41% (940). Those aged 15 up to 64, roughly, the economically active population and actual or potential members of the work force, constitute a total of 65.25% (2,017). Finally, old dependent population consisting of the senior citizens, those aged 65 and over, total 4.34% (134) in all. 

The computed Age Dependency Ratios mean that among the population of Third District, there are 47 youth dependents to every 100 of the working age population; there are 7 aged/senior citizens to every 100 of the working population; and overall, there are 53 dependents (young and old-age) to every 100 of the working population. 

The median age of 25 indicates that half of the entire population of Third District are aged less than 25 and the other half are over the age of 25.

The population of Third District grew from 1,464 in 1990 to 3,091 in 2015, an increase of 1,627 people. The latest census figures in 2015 denote a positive growth rate of 1.34%, or an increase of 209 people, from the previous population of 2,882 in 2010.

Third District is situated at approximately 14.3422, 121.3305, in the island of Luzon. Elevation at these coordinates is estimated at 156.3 meters or 512.8 feet above mean sea level.