|First appearance||"Many Happy Returns"|
|Last appearance||S3:E5 "Show Me the Mummy" (Reoccurring in season 4)|
|Created by||Andrew Cosby
|Portrayed by||Ed Quinn|
|Occupation||Global Dynamics Director of Research|
|Family||Jenna Stark (mother)|
|Children||Kevin Blake (step-son)
Jenna Stark (daughter)
Nathan Stark was a Nobel Prize winning physicist, appointed Director of Research at Global Dynamics following Warren King's dismissal. Cool, calm and calculating, Nathan commanded Eureka's operations with severe efficiency, but gave free rein and authority to GD's scientists, allowing their projects to get out of hand fairly quickly, forcing Jack Carter to step in and save the day. Nathan used his authority to ensure there would be no lasting consequences. Carter and Nathan, as a result, quickly became at odds.
These obvious character flaws were a result of Nathan's deep desire to push science to the point it eventually compromises his personal integrity. Nathan was given his desire for scientific learning by his teacher, mentor and friend Henry Deacon. They somewhat fell out due to Deacon becoming disappointed when Nathan chose administrative duties over using his immense talents to further science. To make up for it, Nathan often gave free rein and political shielding for Deacon's work, as he still looks up to Deacon as a mentor. Nathan also possesses desires for money, prestige and "control of everything" (to rule the world).
Nathan also had an off-again, on-again relationship with Allison Blake. At one point they were married, with Nathan and Allison finding they had much in common, but their relationship broke down due to Nathan being unable to separate work from free time. When Nathan was appointed Director of Research, Allison wasn't happy to have to see and work with him again on a daily basis, though their relationship improved when Nathan finally agreed to a divorce, and they even managed to remain friends. Nathan also appears to maintain a fatherly relationship with his former step-son, Kevin Blake, often insisting he wants only what is best for Kevin. Eventually, Nathan proposes to Allison, and she accepts, much to the distress of Carter.
Nathan also possessed a deeper desire to unravel the mysteries of The Artifact. His work into this was contested by the mysterious group known as The Consortium, whose agent, Beverly Barlowe, secretly sabotaged the experiment, resulting in the apparent deaths of both the Artifact and Kim Anderson. For his incompetence and failure, Nathan was removed from his position and Allison promoted to replace him. Nevertheless, Nathan remained as an advisor. During Stark's removal, when asked to input his password before Blake, his password was 2554766, the ten-key keypad combination corresponding to the letters "Allison" on a phone key-pad.
Upon Eva Thorne's arrival in Eureka, Thorne became Chairman of Global Dynamics, and restored Stark to his position as Director of Research, while Allison was made Director of Operations. The two were to oversee Eureka's development. This partnership and their relationship came to a tragic end on their wedding day, where Nathan disappeared while sealing a time-space anomaly that required him to manually synchronize a particle accelerator with a nuclear clock in order to repair space-time. Though the clock activated and the continuum repaired, Stark dematerialized and vanished. His last words, to Carter, were "I'll see you around, Jack."
In an interview, Ed Quinn said Nathan Stark is inspired by Marvel Comics' Iron Man, Tony Stark, observing that Andrew Cosby, the creator of Eureka, is also the co-founder of independent comic book publisher Boom! Studios and an Iron Man fan. Evidence of such can be seen in the season 1 finale "Once in a Lifetime"; in the alternate timeline version of 2010, Nathan is shown to be the head of "Stark Industries", clearly an homage to the Marvel character of the same surname. The character Tony Stark of Iron Man is the head of his own company also named "Stark Industries". Nathan briefly returns to Eureka as a hallucination of Carter's during Season 4, Episode 8.
- Melissa Hank (April 25, 2007). "Sci-fi made sexy on 'Eureka' (interview with Ed Quinn)". Archived from the original on 2010-09-18.