Chimalpopoca (Classical Nahuatl: Chīmalpopōca [t͡ʃiːmaɬpoˈpoːka] for "smoking shield," modern Nahuatl pronunciation^ⓘ) or Chīmalpopōcatzin (1397–1427) was the third Emperor of Tenochtitlan (1417–1427).

Chimalpopoca was born to the Emperor Huitzilihuitl and Queen Ayauhcihuatl.

Chimalpopoca was crowned in 1417 (some sources say 1416 or 1418), at approximately 20 years old. At that time, Tenochtitlan was a tributary of the Tepanec city of Azcapotzalco, which was ruled by his grandfather Tezozomoc. This alliance, and the Mexicas' position within it, was strengthened by Tenochtitlan's loyalty during Tezozomoc's 1418 war with Ixtlilxochitl I of Texcoco. The conquered city was granted to Tenochtitlan as a tributary.

Nezahualcoyotl, displaced prince of Texcoco, was living in the mountains. Chimalpopoca interceded with Tezozomoc on his behalf, and Tezozomoc agreed to allow Netzahualcoyotl to live in Tenochtitlan under his protection.

In 1426 Tezozómoc assisted Chimalpopoca in the construction of a new aqueduct. This aqueduct was of wood, and ran from the elevated place of Chapultepec to Tenochtitlan.

Chimalpopoca also had a causeway constructed to Tlacopan. The causeway contained openings spanned by wooden bridges, which were removed at night.

Also during his reign he dedicated a stone for sacrifices in the Tlacocomoco section of Tenochtitlan. The conquest of Tequizquiac is also attributed to him.

Chimalpopoca was the son of Huitzilihuitl, the previous ruler, but there are some sources that say he was a son of Acamapichtli, the first ruler of Tenochtitlan, making him Huitzilihuitl's brother. Gerónimo de Mendieta, in his Historia eclesiástica indiana, notes the discrepancy and concludes that Huitzilihuitl, Chimalpopoca and Itzcoatl (Chimalpopoca's successor) must have been brothers, based on his understanding of the Aztec system of succession.