Methane (CH ₄ ) mole fractions from the large semiseasonal Llanos de Moxos wetlands (∼70,000 km ² ) in northern Bolivia were measured by aircraft flights and ground sampling during early March 2019 (late wet season). Daily fluxes of CH ₄ determined from the measurements using box models and inverse modeling were between 168 (± 50) and 456 (± 145) mg CH ₄ ⋅m ⁻² ⋅d ⁻¹ for the areas overflown, very high compared with those of previous Amazon basin studies. If the seasonality of the CH ₄ emissions is comparable to other parts of the Amazon Basin, the region could contribute as much as 8% of annual Amazonian CH ₄ emissions.