Grassius is an online knowledgebase focused on transcription factors and gene regulation in grasses. It brings together information for five species: maize, rice, sorghum, sugarcane, and Brachypodium. The site reports coverage of 9,046 transcription factors and provides species-specific portals for exploring its resources.

Grassius offers several databases and collections, including TFDB, CoregDB, protein–DNA interaction data, and the Maize and Rice TFome collections. Its tools include a gene model ID translation service, a BLAST homology search, and a custom family resource. These features support access to and analysis of information related to plant gene regulation.

The website also introduces the Grassius project and its people, provides data access links, and offers a tutorial and contact information. Its news and publication listings document updates to the knowledgebase and research on plant gene regulatory networks, including work on maize gene regulation and transcription factor collections. Overall, Grassius serves researchers and other users seeking organized resources and tools for studying transcription factors across major grass species.