Which tree has the stoutest tree trunk in the world?

El Árbol del Tule (Spanish for The Tree of Tule) is a tree located in the church grounds in the town center of Santa María del Tule in the Mexican state of Oaxaca, approximately 9 km (6 mi) east of the city of Oaxaca on the road to Mitla. It is a Montezuma cypress (Taxodium mucronatum), or ahuehuete (meaning "old man of the water" in Nahuatl). It has the stoutest tree trunk in the world. In 2001, it was placed on a UNESCO tentative list of World Heritage Sites.

In 2005, its trunk had a circumference of 42.0 m (137.8 ft), equating to a diameter of 14.05 m (46.1 ft), an increase from a measurement of 11.42 m (37.5 ft) m in 1982. However, the trunk is heavily buttressed, giving a higher diameter reading than the true cross-sectional of the trunk represents; when this is taken into account, the diameter of the 'smoothed out' trunk is 9.38 m (30.8 ft). This is slightly wider than the next most stout tree known, a giant sequoia with a 8.90 m (29.2 ft) diameter.

The height is difficult to measure due to the very broad crown; the 2005 measurement, made by laser, is 35.4 m (116 ft), shorter than previous measurements of 41–43 m (135–141 ft).

It is so large that it was originally thought to be multiple trees, but DNA tests have proven that it is only one tree. This does not rule out another hypothesis, which states that it comprises multiple trunks from a single individual.