Mickey Sumner is an English actress. She started her acting career in the 2010s, debuting in the TV series The Borgias. Later, she made her film debut in 2012’s Missed Connections. Sumner gained noticed for her performance in the movie Frances Ha. She went on to have roles in the films Girl Most Likely, CBGB, The Mend, and The End of the Tour. In 2015, she had roles in the movies Anesthesia, This is Happening, and Mistress America. On television, she became known for her recurring role as Katia in the AMC series Low Winter Sun. More recently, she played the role of Beth in the film Marriage Story. She will join the cast of the upcoming series Snowpiercer.