Biographical information
Full name: Cosima Niehaus
Birthplace: San Francisco, California, United States
Birthdate: March 9, 1984
Status: Alive
Age: 34
Residence: Dyad Institute, Toronto, Ontario, Canada
Minneapolis, Minnesota, USA (formerly)
Occupation: Evolutionary Development Biologist (formerly)[1]
Other information
Also known as: Cos (by Sarah)
Auntie Cosima (by Kira)
Sunset (by Kira)
Gender: Female
Hair color: Brown
Eye color: Brown
Skin color: White
Height: 5'4"
Monitor: Delphine Cormier (formerly)
Emi (formerly)
Marital status: in a relationship with Delphine Cormier
Significant Other/s: Delphine Cormier (girlfriend)
Shay Davydov (ex-girlfriend; rebound)
Emi (ex-girlfriend)
Family: Gene Niehaus (adoptive father)
Sally Niehaus (adoptive mother)

Leda clones (sisters/genetic identicals)
Castor clones (genetic brothers)
Kendall Malone (sister/genetic template)
Kira Manning (genetic niece; via Sarah)
Siobhan Sadler (genetic niece; via Kendall)
Donnie (genetic nephew; via Helena)
Arthur (genetic nephew; via Helena)

Series information
Portrayed by: Tatiana Maslany
Season/s: 1, 2, 3, 4, 5
First appearance: "Instinct"
Latest appearance: "To Right the Wrongs of Many"
Appearance count: 46
"Right. I'm 324B21."
—Cosima after Delphine tells her "tag number"[src]

Cosima Niehaus is a Ph.D. student and a clone of American origin on Orphan Black. She, along with fellow clone Alison Hendrix first meet Sarah Manning whilst the latter is under the guise of Beth Childs. The three clones decide to group together to form "Clone Club"[2], whose aim is to find their origin and where they come from. Cosima is involved in a romantic relationship with Delphine Cormier until they break up due to Cosima believing she could not trust her anymore, but they later get back together. Cosima is currently suffering from an unknown respiratory illness originating from her ovaries and reproductive system which causes her to cough up blood.[3]


Early life

Cosima comes from San Francisco, California, and studied at UC Berkeley. She is currently completing her Ph.D. in Experimental Evolutionary Developmental Biology at the University of Minnesota. She was in a relationship with Emi, the lead singer of the band Pythagoras who was also her monitor until they broke up after Cosima moved to Minnesota, believing she can't handle a long-distance relationship.[4]

Beth Childs managed to find her and another clone, Alison Hendrix, through a facial recognition program after Katja Obinger contacted Beth about three other clones in Europe. They have been looking after each other ever since. Meanwhile, the sick Katja, who wanted to see Cosima, whom she knew as a doctor, was asked to submit proof of the European clones' predicament to Beth. Prior to Beth's suicide, it seemed that Cosima constantly called her for updates.

Season 1

In "Natural Selection", after Sarah Manning assumed Beth's identity, Cosima still kept calling Beth's phone.

In "Instinct", Sarah finally picked up after Katja is killed in front of her. Sarah, as Beth, tells Cosima that the German is dead and they both panic. Cosima finally realizes that Katja was telling the truth about someone wanting them dead. Cosima tells Sarah to get rid of the body and get Katja's hair and blood samples. Later, Cosima calls Bet(who is actually Sarah) and tells her to get Katja's briefcase. Cosima calls Sarah back and Sarah stops pretending to be Beth. Cosima says "Just one. I'm a few. No family, too. Who am I?" and hangs up when Sarah doesn't understand. Cosima introduces herself to Sarah at Alison's house.

Cosima meets Sarah Manning in person.

In "Variation Under Nature", Cosima asks Sarah about her past. She tells Alison, who doesn't believe that Beth committed suicide, that Beth was "losing it clinically". Cosima tells Sarah that she wanted to explain the whole clone thing more softly after Alison blurts it out. Cosima meets Felix Dawkins at Alison's house and tells Sarah to bring her Katja's briefcase if she wants more answers. Sarah calls Cosima for help when the police discover Katja's body and she finds out about Sarah's criminal record. Sarah meets Cosima at a local bar on the day she is set to return to Minneapolis for her studies and gives her the briefcase. Cosima tells Sarah that six months ago, Katja contacted Beth and then Beth found Cosima and Alison. Cosima tells Sarah that she needs to keep being Beth to learn more about who's killing them. Cosima tells her to hinder the police's investigation into Katja's identity.

Sarah calls Cosima, now back at school, and tells her that Katja's killer contacted Beth's partner Arthur Bell. Cosima arranges for Alison to teach Sarah how to shoot a gun.

In "Effects of External Conditions", Cosima examines Helena's knife and tries to explain her motives for killing in a video chat with Sarah and Felix. Later, Cosima calls Sarah and tells her that Helena is connected to Maggie Chen, the woman that Beth shot. Cosima deduces that Beth shot her on purpose. Sarah tells Cosima that Helena was at the police station and wants to meet her. Cosima explains that Helena is on a religious crusade to kill the clones because Helena believes them to be abominations.

In Conditions of Existence, Cosima explains, over video chat, to Sarah, Felix and Alison that the object in her mouth was an electrode from an EEG helmet which monitors electrical activity in the brain. Cosima says that if it was her experiment she'd put an observer close to the subject.

In the lab, Cosima is testing the clone samples. She asks Scott to help her but doesn't tell him what it's for. She notices an upset Delphine who leaves behind her report card. Cosima sneaks a peek at it and then follows Delphine, finding her crying. They introduce themselves properly and clearly hit it off. Cosima tells her that she's studying evo-devo (evolutionary development).

Cosima calls Sarah after Felix plays her the recording of Paul and Olivier and tells her that it's a double blind so Paul may not even know he's watching a clone.

In Variations Under Domestication, Sarah tells Cosima that she was right about Paul as Cosima walks through the library and bumps into Delphine. Cosima tells Sarah she has a monitor dilemma too and Sarah tells her to stay away and "stick to the science". Cosima is annoyed, saying "What am I, the geek monkey, now?" Cosima walks over to Delphine who tells her about a lecture - Neolution by Dr. Aldous Leekie - and asks her to come with her. After the talk, Dr. Leekie chats with Cosima and Delphine and tells them to have a look at Dyad. Cosima steals two bottles of wine and her and Delphine run across campus, holding hands. Cosima tells Delphine that she is going to get her so baked one day. Delphine kisses her on each cheek and leaves.

In Parts Developed in an Unusual Manner, Sarah again tells Cosima to stay away from Delphine over video chat. Cosima says that this is different than Alison and Donnie as she's the one monitoring Delphine. Later, Sarah phones Cosima to tell her Helena's back. Cosima asks if Sarah knows Dr. Leekie, saying he's the poster boy for Neolution. Sarah tells her that Olivier owns a club called Neolution. Cosima tells Sarah that she went with Delphine to one of Leekie's lectures causing them fight and hang up. Delphine arrives at Cosima's apartment and she's not ready telling her, "I'm kind of always late, though, so, kind of always sorry". They go to dinner and Delphine tells her she should have left her boyfriend when she left Paris and that she was the one who stopped him joining her. Cosima says "You're the asshole?" She invites Dr. Leekie to join them, with Cosima unimpressed.

Cosima uncovers Delphine and says she feels betrayed by Delphine.

Dr Leekie approaches Cosima and offers her a job at Dyad Institute along with her complete genome sequence. She arrives at Felix's place where she's coughing up blood. Delphine arrives shortly after and tells her that the genome Leekie gave is not complete, the marker is scrubbed out. With the help of Delphine she manages to decode her marker. It is actually a patent with the sentence "This organism and derivative genetic material is restricted intellectual property" written in DNA.

Season 2

Season 3

In the Season 3 premiere, Cosima is living in Felix's loft and appears to be healthier. She speaks to Kira about her dream (from the Season 2 finale) and her "coming back" to Kira. Their conversation is interrupted by Delphine, who tells Cosima that she is taking over some of Rachel's duties at Dyad, effectively putting her in charge. She also breaks up with Cosima, and tells her that she is keeping her promise to love and care for each Leda clone equally. She tasks Cosima with finding a cure for herself and her sisters, before tearfully leaving the loft. Later that day, Scott comes to perform a checkup. Cosima shows him Professor Duncan's key imbedded in his copy of The Island of Dr. Moreau while telling him to keep the information secret until they can both decipher the information.

In "Transitory Sacrifices of Crisis", Scott is still performing regular checkups on Cosima's condition and is surprised by her significantly improved test results. Both he and Cosima are unable to explain her sudden improved health though Cosima begins to explore potentially spiritual explanations. Back at Dyad, Cosima and Scott meet with Dr. Nealon. They discuss Rudy's escape from Marion Bowles' basement as well as the lost Leda genome. Dr. Nealon informs them of the origins of Project Castor and Leda as well as the impossibility of finding the original tissue donors, whose records were falsified and destroyed by both Susan and Ethan Duncan. Later, Cosima helps Sarah by researching the mythology of Castor, the warrior horsemen, thereby associating the Project Castor clones as, "the perfect ghost soldiers". She also tells Sarah to speak with Siobhan so that they can find Paul and ultimately Helena.

Season 4

Season 5

Personality and traits

Cosima is an eccentric, queer, tattooed geek girl with a scientific mind verging on genius. She's dependable, incredibly caring, brave, driven to find answers and, like Sarah, adaptable to extreme circumstances. She also tends to diverge on scientific topics and can talk relatively fast when she gets excited.

Physical appearance

Cosima usually wears her hair in intricate dreadlocks. In addition to her tattoo, Cosima also has a nose ring. According to Felix, Cosima has bigger breasts than Sarah and is apparently more attractive.


  • Her tag number, the number that identifies her among the clones, is 324b21.
  • Her IQ is 147.[5]
  • In Effects of External Conditions, she is shown to be smoking marijuana. She later admits to Delphine that she only smokes this and never cigarettes in Variations Under Domestication.
  • She is shown to have a taste for wine as she was seen having a glass in a bar in Variation Under Nature and stealing two bottles from Leekie's reception in Variations Under Domestication.
  • Her laptop is covered with a laptop skin designed with multi-colored DNA strands and carbon rings.
  • The reason that Cosima wears glasses and her clones do not is due to the fact that her sight degenerated due to her environment and conditions. She just studies too much. (#geekmonkey) [6]
  • Cosima was named after Orphan Black's own Science Consultant, Cosima Herter.[7]
  • In an interview, Tatiana states that the writers mentioned to her that Cosima was bisexual, though Tatiana feels that Cosima simply just loves people.[8] Despite this, Cosima refers to herself as a lesbian in Community of Dreadful Fear and Hate whilst making a speech as Alison.
  • The actress, Tatiana Maslany, who plays the clones, uses music to differentiate the clones. Her playlist for Cosima is electronica, including artists such as Diplo and Grimes. Maslany has described it as "beeps and boops kind of stuff."[9]
  • Cosima's DYAD Institute employment record shows her ID tag as 7274-7342-CS.[1]



Season 1 appearances
Natural Selection Instinct Variation Under Nature Effects of External Conditions Conditions of Existence
Variations Under Domestication Parts Developed in an Unusual Manner Entangled Bank Unconscious Selection Endless Forms Most Beautiful
Season 2 appearances
Nature Under Constraint and Vexed Governed by Sound Reason and True Religion Mingling Its Own Nature With It Governed As It Were By Chance Ipsa Scientia Potestas Est
To Hound Nature in Her Wanderings Knowledge of Causes, and Secret Motion of Things Variable and Full of Perturbation Things Which Have Never Yet Been Done By Means Which Have Never Yet Been Tried
Season 3 appearances
The Weight of This Combination Transitory Sacrifices of Crisis Formalized, Complex, and Costly Newer Elements of Our Defense Scarred by Many Past Frustrations
Certain Agony of the Battlefield Community of Dreadful Fear and Hate Ruthless in Purpose, and Insidious in Method Insolvent Phantom of Tomorrow History Yet to Be Written
Season 4 appearances
The Collapse of Nature Transgressive Border Crossing The Stigmata of Progress From Indistinct to Rational Control Human Raw Material
The Scandal of Altruism The Antisocialism of Sex The Redesign of Natural Objects The Mitigation of Competition From Dancing Mice to Psychopaths
Season 5 appearances
The Few Who Dare Clutch of Greed Beneath Her Heart Let the Children and Childbearers Toil Ease For Idle Millionaires
Manacled Slim Wrists Gag or Throttle Guillotines Decide One Fettered Slave To Right the Wrongs of Many



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