This chapter introduces multichannel nonnegative matrix factorization (NMF) methods for audio source separation. All the methods and some of their extensions are introduced within a more general local Gaussian modeling (LGM) framework. These methods are very attractive since allow combining spatial and spectral cues in a joint and principal way, but also are natural extensions and generalizations of many single-channel NMF-based methods to the multichannel case. The chapter introduces the spectral (NMF-based) and spatial models, as well as the way to combine them within the LGM framework. Model estimation criteria and algorithms are described as well, while going deeper into details of some of them.