Lois Lane is a fictional character on the television series Smallville; she was portrayed continually by Erica Durance since her first appearance in the season four premier "Crusade" to the series finale. Durance began as a guest star in season four but was promoted to series regular status beginning in season five. The character of Lois Lane, first created for comic books by Jerry Siegel and Joe Shuster in 1938 to be the love interest for Clark Kent and his alter-ego Superman, was adapted to television in 2001 by Alfred Gough and Miles Millar - this is the fourth time the character has been adapted into a live-action television series.

In Smallville, Lois comes to town to investigate the apparent death of her cousin Chloe Sullivan at the start of the fourth season. After finding Chloe still alive, Lois is forced to enroll in Smallville High to complete the remaining credits of high school she failed to achieve. As the series progresses, her interest in journalism grows, first writing a couple of articles for the Smallville High Torch in season four, landing a job at the Inquisitor in season six, and finally being hired at the Daily Planet in season seven. Throughout seasons four, five, six and seven, Lois's relationship with Clark Kent is depicted more as a brother and sister relationship, with the two characters often butting heads and teasing each other. By season eight, Lois begins to realize that she is falling in love with Clark, and by season nine the two become an official couple. During season ten the relationship goes through several milestones and midseason the pair get engaged. It's not shown but sometime between the series finale and the Arrowverse crossover "Crisis on Infinite Earths" they officially get married and are happily married with two unnamed daughters.

Series developers Gough and Millar had always envisioned bringing the character of Lois Lane to Smallville, but it was not until the end of season three that the creative team had the right storyline to bring her in. Erica Durance was hired to portray the iconic female reporter from the comic books. Smallville's interpretation of Lois was designed to embody similar traits to that of various leading female characters in the film. Described as "fiercely independent", critics have favorably compared this version of Lois Lane against the other live-action performances of the character in both film and television.

Lois Lane makes her first appearance in season four's "Crusade" when she comes to Smallville investigating the death of her cousin Chloe Sullivan (Allison Mack). While investigating Chloe's death with Clark Kent (Tom Welling) in "Gone", the pair uncover the truth that Chloe is still alive, but in witness protection until Lionel Luthor's trial, the man she is testifying against with evidence that he orchestrated the death of his own parents. Lionel (John Glover) discovers the truth and sends someone to kill her, but Lois and Clark stop the would-be killer, allowing Chloe to testify. Before Lois can leave Smallville, her father (Michael Ironside) informs her that she failed to achieve all of her high school credits and that he has enrolled her in Smallville High so that she can complete her twelfth-grade year. Staying with the Kents, Lois begins attending Smallville High. In "Faςade", Chloe convinces her to become a reporter for the Torch in an effort to help Lois earn some of her remaining credits. With Lex Luthor's (Michael Rosenbaum) help in the episode "Devoted", Clark manages to get Lois her remaining credits ahead of schedule so that she can attend Metropolis University, and vacate his bedroom.

In season five's "Fanatic", Jonathan Kent (John Schneider), who is running for the state senate, asks Lois to be his campaign manager after witnessing her take charge against his former campaign manager, whom Jonathan fires when he published a statement that goes against Jonathan's values. In "Fragile", Lois continues her duties under Martha Kent (Annette O'Toole), who is requested by the Governor to take Jonathan's place after he suffers a fatal heart attack. In season six's "Sneeze", Lois discovers an interest in journalism after she is almost struck by a barn door that falls out of the sky while she is jogging. Her story is bought by the Inquisitor, a tabloid newspaper that gives her a job as a reporter. In "Wither", she begins a romantic relationship with billionaire Oliver Queen (Justin Hartley), who, unbeknown to her, masquerades at night as the vigilante Green Arrow. Queen's "job" as Green Arrow often gets in the way of their relationship. In "Hydro", Lois deduces that Oliver is Green Arrow, setting up an elaborate scheme to prove it. Clark and Oliver are wise to her plan, however, and Clark dresses up as Green Arrow to throw Lois off Oliver's trail. When Oliver is forced to leave Metropolis to track down all of Lex's experimental facilities, in the episode "Justice", his relationship with Lois comes to an end. In season six's "Prototype", Lois discovers that Lex has been doing experimental research on army soldiers, one of which was her best friend. As a result, Lois decides in "Phantom" to begin looking into Lex's LuthorCorp projects.

In season seven's "Kara", while looking into Lex's research projects, Lois discovers an alien spaceship. Her attempt to craft a news story out of the situation lands her a job at the Daily Planet - in the basement alongside her cousin Chloe. While at the Daily Planet, Lois begins a new relationship with her editor Grant Gabriel (Michael Cassidy) in the episode "Wrath". Their relationship comes under scrutiny from Chloe and Lex in "Blue", with Chloe seeing it as a reason for co-workers to doubt Lois's true ability as a journalist, and Lex believing it will jeopardize the secret of Grant's true identity. In "Gemini", the two finally agree to part ways. In the season eight premiere, Lois believes that Lex is responsible for Chloe's arrest by the Department of Domestic Security, and goes to his mansion to search his files for her location. She eventually discovers Chloe's whereabouts and arrives, alongside Clark, to save her. In "Plastique", Lois takes Clark under her wing—teaching him how to be a reporter—after he accepts an internship at the Daily Planet, sitting at the desk directly across from Lois. Her feelings for Clark become stronger as the season progresses, admitting in the episode "Committed" that she is in love with Clark, and stating to Oliver in the episode "Bride" that she has never felt this way about someone before. In the same episode, she almost shares a kiss with Clark before being interrupted by the arrival of Clark's ex-girlfriend Lana Lang (Kristin Kreuk). In the season eight finale, Lois and Tess Mercer (Cassidy Freeman), Lex Luthor's handpicked successor to LuthorCorp, get into a physical fight at the Daily Planet. During the fight, Lois picks up a Legion ring that falls out of Clark's desk and is instantly transported to another time and place.

In season nine, Lois returns from the future suffering from visions of Earth having been overrun by aliens, led by Zod (Callum Blue). This season, Lois and Clark officially begin a romantic relationship, while Lois also begins assisting "The Blur" in his heroic endeavors. Lois's trust in Clark is shaken when she thinks Clark is jealous of her relationship with "The Blur", and that he does not understand her need to find value in her own life's work. Ultimately, Lois deduces Clark's true identity as "The Blur" in the season nine finale. Lois and Clark's relationship reaches its peak in the tenth and final season. Clark finally confesses his secret to her in "Isis" and they begin their relationship again free of secrets. He proposed marriage in "Icarus". In the episode "Beacon", with Chloe's help, Lois rallies faithful fans of "The Blur" and repeals the Vigilante Registration Act (VRA), helping Clark and the Justice League preserve their secret identities. In "Masquerade" and "Booster", Lois convinces Clark to develop an alter-ego as a way of hiding his true identity as the heroic "Blur". In the episode "Prophecy", Lois is given Clark's powers for a day, as a wedding gift by his biological father Jor-El, and realizes that the devotion they have for each other is Clark's greatest weakness, and calls off the wedding. In the series finale, Clark convinces Lois that her being in his life makes him stronger, but the ceremony is interrupted by Darkseid's sudden invasion of the Earth. Lois convinces the US military not to bomb Darkseid's homeworld of Apokolips, allowing Clark to finally embrace his destiny and defeat Darkseid himself.

Series developer Al Gough contends that it was always the producer's intention to bring in the iconic Lois Lane, but they needed a good reason to do it—Chloe's supposed death at the end of season three appeared to be that reason. Gough explains that, when casting for the role, they looked to Margot Kidder—Lois Lane in the Superman film series—for inspiration. They wanted an actress who was "pretty", "smart", and who came with some "wit". Dozens of actresses auditioned for the role of Lois Lane, but it was not until a tape from Erica Durance showed up that everyone felt that they had found the right Lois. Executive producer Greg Beeman described Durance as tough, sexy and direct for her role. Another plus, according to Beeman, was the chemistry between Durance and Tom Welling. Durance came on set that first afternoon and the two hit it off, becoming friends and developing a brother/sister relationship on the set.