Lyndsy Marie Fonseca (born January 7, 1987 in Oakland, California) is an American actress.
- The Young and the Restless (20012005) as Colleen Carlton
- Boston Public (2003) as Jenn Cardell
- Malcolm in the Middle (2004) as Olivia
- NYPD Blue (2004) as Madison Bernstein
- How I Met Your Mother (20052014)note as Penny Mosby
- Big Love (20062009) as Donna
- Phil of the Future (2006) as Kristy
- CSI (2007) as Megan Cooper
- House (2007) as Addie
- Heroes (2007) as April
- Desperate Housewives (20072009) as Dylan Mayfair
- Nikita (20102013) as Alexandra "Alex" Udinov
- Agent Carter (20152016) as Angie Martinelli
- Kick-Ass (2010) as Katie Deauxma
- Hot Tub Time Machine (2010) as Jenny Steadmeyer
- The Ward (2010) as Iris
- Kick-Ass 2 (2013) as Katie Deauxma
- Aloof Dark-Haired Girl: Her most common roles are either a Deadpan Snarker or a straight-out Ice Queen. Sometimes both.
- But Not Too Foreign: Her father is of Portuguese descent, and her mother is of half Portuguese ancestry.
- Former Child Star: Downplayed, if not subverted. Not only did she started as a teenager (13), but she also has regular work.
- Playing Against Type: Her character in Agent Carter is far from her usual Aloof Dark-Haired Girl gigs.
- Spell My Name with an "S": It is indeed spelled "Lyndsy", not the more traditional "Lyndsey".
- Typecasting: She's usually cast as an Aloof Dark-Haired Girl (see above). Very much averted in Agent Carter.