Ainsley Hayes is a fictional character played by Emily Procter on The West Wing, an American serial political drama. Primarily appearing in the second and third seasons for a total of twelve episodes, Ainsley served as the Associate White House Counsel under the show's president, Josiah Bartlet. Reception for Ainsley has ranged from mixed to positive; she is characterized as smart and flirtatious, but also vulnerable to sexism from other characters.

Ainsley Hayes first appears in The West Wing's second season, in the 2000 episode "In This White House". Emily Procter, then a struggling actress in a Beverly Hills apartment, read for the role. She later told Empire magazine that she had driven a run-down car to the audition. She also recalled that her "strange, pulled-together outfit", which included purple pants, caused her to have to come back and repeat the audition.

Ainsley was originally scripted as a Republican from the western state of Montana, but Procter read her lines with a Southern accent. On Procter's first day of work, the show's creator, Aaron Sorkin, asked her whether she would like the character to be from North Carolina instead. She accepted, later remarking that it was "such a sweet thing to do".

Sorkin wrote in the official companion book to The West Wing that Ainsley was created to attract younger women to the show. However, he also commented that she was intended to counter a trend he perceived at the time in which "young, blond, and leggy" Republican women frequently worked as unintelligent commentators. Indeed, Ainsley's character has drawn multiple comparisons to real-life American political commentator Ann Coulter, but Sorkin counters that "Ainsley Hayes has an extraordinary sense of duty. When her president asks her to serve, she agrees, which makes her perfect for us". In Ainsley's first scene, the other characters assume she embodies the stereotype, with Sam Seaborn referring to her as a "young, blonde, leggy Republican". The characters are then proved mistaken when Ainsley reveals her prowess as a debater.

Ainsley never became a regular character on the show; Sorkin was concerned about the feasibility of including another character in every episode, telling Empire magazine that he "already had eight mouths to feed". In the end, Sorkin regretted his decision to not incorporate Ainsley, calling it the biggest mistake he had made in the show's seven-season run. For her part, Procter had expressed a desire to become a regular character early on. She later commented that it was something of a miscommunication, stating that "If I had in any way known that this was a possibility, I would have stayed there forever! They would've had to kick me out!" Ainsley's character disappeared after the third season, with a reappearance in the seventh season episode "Requiem"; she appeared in a total of twelve episodes. After her time on The West Wing, Procter was quickly picked up for a part on CSI: Miami.

On The West Wing, Ainsley Hayes serves as the Associate White House Counsel. She was introduced to the show on a fictional political television program known as Capitol Beat. Despite demeaning comments from those around her, Ainsley gives Sam Seaborn a humiliating defeat in the "spin battle"; the president, Democrat Josiah Bartlet, chooses to hire Ainsley, sensing her intellect and sense of civic duty despite her conservatism. Ainsley had a promising future as a Republican political pundit, but, as she remarked to the White House counsel furious over her hiring, she wanted to "roll up [her] sleeves, set aside partisanship, and say 'what can I do?'"

Ainsley is shown to have, as one reviewer put it, a "smart, conservative, principled voice". In "The Lame Duck Congress", Ainsley dresses down Republican staffers who question her viewpoint on a nuclear test ban treaty, with Ainsley countering that they themselves don't necessarily oppose the treaty, but they want to score political points by killing the treaty's ratification. In another episode, when Sam asks Ainsley to summarize a 22-page paper on a commerce amendment in two pages, Ainsley reverses Sam's position and convinces him of her own viewpoint; she also argues with Sam on the Equal Rights Amendment in the second-season episode "17 People", calling it "humiliating" to believe that a law is needed to declare a woman equal to a man. In another episode, Ainsley prevents Sam from disclosing privileged information to force an oil company to pay for a cleanup, which she argued could have gotten him disbarred.

Ainsley and Sam also engage in flirtation over the course of the show; for example, in "Bartlet's Third State of the Union", Ainsley asks Sam to dance with her while wearing a robe and playing "Blame It on the Bossa Nova" in her office. The flirtation led Steve Heisler of The A.V. Club, in a 2010 episode-by-episode review of the show, to quip "when are they going to bone already?" Author Patrick Webster, in a footnote, speculates that the two characters were having sex already, in considering the second-season episode "17 People".