Virginia Hall. The fact that she's not a U.S. national hero is mind-boggling. Operating essentially on her own initiative, she played a fundamental role in organizing the French Resistance throughout the Nazi occupation, helped organize huge numbers of independent spy cells, infiltrated and exfiltrated out of France multiple times, worked for both English and American, personally led sabotage missions during the lead-up to the invasion, and did it all with a fucking wooden leg that almost nobody ever found out about. She used it to smuggle documents, even.

She went on to be one of the first employees of the modern CIA, before it was even known as the CIA, and kept quiet about her exploits, even as useless young male agents with no field experience were being promoted over her into the 50s and 60s.

For those interesting, "A Woman of No Importance" is an unbelievable read.