Yaxha (or Yaxhá in Spanish orthography) is a Mesoamerican archaeological site in the northeast of the Petén Basin in modern-day Guatemala. As a ceremonial centre of the pre-Columbian Maya civilization, Yaxha was the third largest city in the region and experienced its maximum power during the Early Classic period (c. AD 250–600). The city was located on a ridge overlooking Lake Yaxha. The name of the city derives from the Mayan for "blue-green water"; it is a notable survival of a Classic period place-name into the modern day. The Yaxha kingdom is estimated to have covered an area of 237 square kilometres (92 sq mi) and to have had a peak population of 42,000 in the Late Classic period of Mesoamerican chronology.

Yaxha had a long history of occupation with the first settlement being founded sometime in the Middle Preclassic period (c. 1000–350 BC). It developed into the largest city in the eastern Petén lakes region during the Late Preclassic (c. 350 BC – AD 250) and expanded into an enormous city during the Early Classic (c. AD 250–600). At this time, in common with other sites in Petén, it shows strong influence from the distant metropolis of Teotihuacan in the Valley of Mexico. It was eclipsed during the Late Classic (c. AD 600–900) by neighbouring Naranjo but was never completely dominated. The city survived well into the Terminal Classic (c. 800–900) but was abandoned by the Postclassic period (c. 900–1525).

The ruins of the city were first reported by Teoberto Maler who visited them in 1904. The site was mapped in the 1930s and again in the 1970s and stabilisation work began in the late 1980s. The ruins include the remains of more than 500 structures with a number of major archaeological groups linked by causeways. Approximately 40 Maya stelae have been discovered at the site, about half of which feature sculpture.

The name Yaxha derives from the Mayan yaxa', which means "blue-green water". Yaxha is notable for the survival of its toponym from the Classic period, when it was a thriving city. David Stuart first proposed that the emblem glyph of the site should be read Yax-ha and that the name of the city (and the lake) is of ancient origin.

Located in the modern-day department of Petén, northern Guatemala, it is approximately 30 kilometres (19 mi) southeast of Tikal; Yaxha is situated on the north shore of Lake Yaxha; the ruins extend roughly 3 kilometres (1.9 mi) along a hilltop parallel to the lake shore. The ruins fall within the borders of the Yaxha-Nakum-Naranjo National Park, which encompasses an area of 37,160 hectares (143.5 sq mi) and incorporates the remains of four ancient Maya cities: Yaxha, Topoxte, Nakum and Naranjo, as well as 10 intermediate sites and more than 280 smaller settlements.

All dates A.D.

Yaxha was already significant in the Late Preclassic (c. 350 BC – AD 250), and was a large site as far back as the Middle Preclassic (c. 1000–350 BC). Archaeological investigations indicate that the earliest, Middle Preclassic, settlement was in what developed into the southern and western sectors of the city. In the Late Preclassic the city became the largest settlement in the Yaxha-Sacnab basin, with a marked increase in population and in construction activity.

The city reached the height of its power during the Early Classic period of Mesoamerican chronology (c. AD 250–600), during which period the city expanded enormously. The city's Early Classic monuments are poorly preserved, meaning that the history of its period of maximum power is poorly understood. The influence of the distant metropolis of Teotihuacan in the Valley of Mexico is evident in Early Classic imagery following Teotihuacan's decisive intervention at Tikal in AD 378. At the end of the Early Classic, seismic activity caused movement of the Yaxha Fault, resulting in damage to buildings in the East Acropolis. The same earthquake appears to have caused damage across the city and at neighbouring Nakum. The earthquake may have resulted in the temporary abandonment of the East Acropolis.