Grantia is een geslacht van sponsdieren uit de klasse van de Calcarea (kalksponzen).
Soorten Grantia aculeata Urban, 1908 Grantia arctica (Haeckel, 1872) Grantia atlantica Ridley, 1881 Grantia beringiana Hozawa, 1918 Grantia canadensis Lambe, 1896 Grantia capillosa (Schmidt, 1862) Grantia comoxensis Lambe, 1893 Grantia compressa (Fabricius, 1780) Grantia cupula (Haeckel, 1872) Grantia extusarticulata (Carter, 1886) Grantia fistulata Carter, 1886 Grantia foliacea Breitfuss, 1898 Grantia genuina Row & Hozawa, 1931 Grantia glabra Hozawa, 1933 Grantia harai Hozawa, 1929 Grantia hirsuta (Topsent, 1907) Grantia indica Dendy, 1913 Grantia infrequens (Carter, 1886) Grantia intermedia Thacker, 1908 Grantia invenusta Lambe, 1900 Grantia kempfi Borojevic & Peixinho, 1976 Grantia kujiensis Hozawa, 1933 Grantia laevigata (Haeckel, 1872) Grantia mexico Hôzawa, 1940 Grantia mirabilis (Fristedt, 1887) Grantia monstruosa Breitfuss, 1898 Grantia nipponica Hozawa, 1918 Grantia phillipsi Lambe, 1900 Grantia primitiva Brøndsted, 1927 Grantia ramulosa Dendy, 1924 Grantia scottia (Jenkin, 1908) Grantia singularis (Breitfuss, 1898) Grantia socialis Borojevic, 1967 Grantia strobilus (Haeckel, 1872) Grantia stylata Hozawa, 1929 Grantia tenuis Urban, 1908 Grantia transgrediens Brøndsted, 1931 Grantia tuberosa Poléjaeff, 1883 Grantia uchidai Hozawa & Tanita, 1941 Grantia vosmaeri Dendy, 1893 Grantia waguensis (Hozawa, 1940)