James Cecil Hatlo (September 1, 1897 – December 1, 1963), better known as Jimmy Hatlo, was an American cartoonist who in 1929 created the long-running comic strip and gag panel They'll Do It Every Time, which he wrote and drew until his death in 1963. Hatlo's other strip, Little Iodine, was adapted into a feature-length movie in 1946.

In an opinion piece for the July 22, 2013, edition of The Wall Street Journal, "A Tip of the Hat to Social Media's Granddad", veteran journalist Bob Greene characterized Hatlo's daily cartoons, which credited readers who contributed the ideas, as a forerunner of Facebook and Twitter. Greene wrote: "Hatlo's genius was to realize, before there was any such thing as an Internet or Facebook or Twitter, that people in every corner of the country were brimming with seemingly small observations about mundane yet captivating matters, yet lacked a way to tell anyone outside their own circles of friends about it. Hatlo also understood that just about everyone, on some slightly-below-the-surface level, yearned to be celebrated from coast to coast, if only for a day."

Hatlo was born in East Providence, Rhode Island, on September 1, 1897. His father, James M. Hatlow, a printer, was an immigrant from the Orkney Islands of Scotland. The original spelling of the family name became an inconvenience when, as a budding sports cartoonist, Hatlo fashioned a trademark signature with the "H" drawn as stylized goal posts and the "o" as a descending football. He shrank the "w" into a small apostrophe in the signature but otherwise dropped it entirely.

When he was a small child, the family moved to Los Angeles. As a young man, Hatlo began doing incidental artwork and engravings for local newspapers during an era when halftone reproduction of photographs was still limited.

When the United States entered World War I, Hatlo went to Kelly Field, hoping to become an aviator despite his poor eyesight. Instead he became a Spanish flu casualty and missed the war entirely.

He relocated to San Francisco following the war and worked for both the San Francisco Call & Post and the San Francisco Evening Bulletin. The two papers later merged as the San Francisco Call-Bulletin, part of William Randolph Hearst's publishing empire. Hatlo at first drew "travelogues" for automobile advertising. These illustrated maps promoted auto travel (and thus auto sales). On the strength of his talent, he soon managed to work his way into editorial cartooning and then sports cartooning. His sports cartoon for the Call-Bulletin was Swineskin Gulch.

His break came when a shipment of panels from syndicated cartoonist Tad Dorgan failed to arrive in the mail. Hatlo was pressed into service to create something to fill the space. What resulted was They'll Do It Every Time, an instant hit with San Francisco readers. After several days, he began to run short on ideas. Various people—including Pat Frayne, Hatlo's managing editor at the time, and Scoop Gleason, his sports editor—later claimed credit for what happened next; even so, it may have been Hatlo himself, to adopt the tactic of asking readers to submit their own ideas for the cartoons. Whatever the source, this gambit was a huge success. Hatlo picked the best submissions, and credited each contributor by name, in closing the such cartoon with a box that read, "Thanx and a tip of the Hatlo Hat to...", followed by the submitters's name.

They'll Do It Every Time became a fixture in the Call-Bulletin. It soon caught the attention of Hearst and was picked up by Hearst's King Features Syndicate. His supplemental panel, The Hatlo Inferno, which depicted life in Hell, ran in tandem with They'll Do It Every Time for five years (1953–58).