C. tumescens may refer to:
Chonetes tumescens, an extinct species of brachiopod. Chorigyne tumescens, a species of plant. Chrysogaster tumescens, a species of hoverflies. Clypeaster humilis (synonym Clypeaster tumescens), a species of sea urchin. Corymbia tumescens, a species of tree. Cymbella tumescens, a species of diatom. Cymus tumescens, a species of true bug. Terrabacter tumescens (formerly Corynebacterium tumescens), a Gram-positive bacterium.