'Aquatic fungi (freshwater and marine) the topic covered in this monograph includes the kingdom Fungi (Kirk et al. 2008) and taxa traditionally treated as fungi (e.g., Oomycetes); they comprise diverse fungal groups including Ascomycetes, Basidiomycetes, Chytridiomycetes, and Zygomycetes (Shearer et al. 2007). Aquqtic fungi play an essential role in ecosystems, which has been thoroughly reviewed by Krauss et al. (2011). Aquatic environment harbor many taxonomically unknown fungi. About 3000 fungal species and 138 Saprolegnialean (Oomycetes) species have been reported from aquatic habitats (Shearer et al. 2007). Hitherto detailed compilation of Freshwater and Marine fungi of India are however very meager. Thus, this monographic work makes an effort to provide a detailed compilation of information on substrate range, state-wise distribution and references of Freshwater and marine fungi of India.