The missions, which have each been awarded $500m (£352m) in funding, are due to launch between 2028 and 2030.
Nasa administrator Bill Nelson said the missions would offer the "chance to investigate a planet we haven't been to in more than 30 years".
The last US probe to visit the planet was the Magellan orbiter in 1990.
However, other spacecraft - from Europe and Japan - have orbited the planet since then.
The missions were picked following a peer review process and were chosen based on their potential scientific value and the feasibility of their development plans.
"These two sister missions both aim to understand how Venus became an inferno-like world, capable of melting lead at the surface," Mr Nelson said.
Venus is the second planet from the sun and the hottest planet in the solar system with a surface temperature of 500C - high enough to melt lead.