According to one embodiment, an active material is provided. The active material includes active material particles. The active material particle includes a core particle and a shell layer which covers at least a part of a surface of the core particle. The core particle contains a monoclinic or orthorhombic niobium-titanium composite oxide. The shell layer contains a compound which is at least one compound selected from the group consisting of a lithium-titanium composite oxide, an Nb-containing lithium-titanium composite oxide, a lithium-niobium composite oxide, a lithium phosphate, and an Nb-containing lithium phosphate. The compound has a composition different from that of the monoclinic or orthorhombic niobium-titanium composite oxide.