"Sgt. Wilson's Little Secret" is an episode in the British tv comedy series Dad's Army. It was originally transmitted on Saturday 22 March 1969.

Tensions rise when Sgt. Arthur Wilson’s close friendship with Mavis Pike, a local bank clerk, starts sparking rumors in the village of Walmington-on-Sea. The gossip takes a surprising turn when Mavis reveals that she’s pregnant, leading the Home Guard members—and especially Captain Mainwaring—to assume that Wilson is the father. Mainwaring, proud of his moral standards, is scandalized by Wilson's supposed indiscretion and can't resist meddling in what he believes is Wilson's personal responsibility.

As the rumors spread, the platoon is abuzz with opinions on Wilson's presumed impending fatherhood. Wilson, in his typically laid-back and reserved manner, seems indifferent to the speculation, much to Mainwaring’s annoyance. The situation reaches a climax during the Home Guard’s maneuvers, where the misunderstandings and assumptions pile up, leading to comedic mishaps. Eventually, the truth is revealed, and the episode ends on a note of camaraderie, as the misunderstanding is humorously cleared up, much to the relief of everyone involved.

When Mrs Pike plans to take in an evacuee, Wilson misunderstands and thinks that she is pregnant. Mainwaring orders him to marry her, and just as the preparations are under way, Mrs Pike leads in a 10-year-old Cockney evacuee also named Arthur. The wedding doesn't take place.

Until 2001, when two "lost" episodes ("Operation Kilt" and "The Battle of Godfrey's Cottage") were found, "Sgt. Wilson's Little Secret" was the only episode surviving from the second series.

Even though in this episode it becomes common knowledge (erroneously as it turns out) that Sergeant Wilson and Mrs Pike are expecting a baby and so have decided to get married, from the next episode onwards things appear to have been retconned and as a consequence their “relationship” becomes a secret again to everyone, including Frank Pike.

• Croft, David; Perry, Jimmy; Webber, Richard (2000). The Complete A-Z of Dad's Army. Orion. ISBN 0-7528-4637-X.

• "Sgt. Wilson's Little Secret" at IMDb