Nancy Wheeler is a fictional character from the Netflix television show Stranger Things, portrayed by American actor Natalia Dyer. She is the sister of Mike Wheeler, the girlfriend of Jonathan Byers, and the ex-girlfriend of Steve Harrington. Nancy starts investigating the disappearance of Will Byers when her friend Barbara also goes missing. She teams up with her future boyfriend Jonathan Byers to investigate Will and Barbara's disappearance, which leads to her discovery of the Upside Down, an alternate dimension.