Megarhyssa atrata, also known as the black giant ichneumonid wasp, is a species of large ichneumon wasp.

It is known from North America,[1] where it is found from Quebec, Michigan, Ohio and North and South Carolina to Florida.

[2] Adults are on wing from May to July.

[citation needed] The larvae are parasitoids of the larvae of the woodwasp Tremex columba in dead deciduous trees.

[3] Female M. atrata burrow into wood with their ovipositor while secreting a substance that breaks down the wood.