Tetrastichus is a genus of hymenopteran insects of the family Eulophidae. Tetrastichus planipennisi is a parasitoid of the emerald ash borer, a wood boring insect native to Asia which is an invasive species in North America. T. planipennisi is being evaluated as a biological control agent. The genus Tetrastichus parasitizes many different species of Lepidoptera, such as Pyralis farinalis.