The idea of Brahman is that He is a "Great World Soul"; he is a single entity (monotheism) that encompasses the entire universe (pantheism). This seems simple enough, until you bring in the concept that he has multiple different variations of his existence: Vishnu, Shiva, and many, many, many, many, many other Gods (polytheism?). One could argue that, since it is the same God with multiple different variations, it is similar to the Christian trinity; hundreds of gods within one World Soul. Therefore, it is not really polytheism. One could also argue that pantheism is technically also monotheism. So I would say that Hinduism is a pantheistic religion.

What are your thoughts?