In 1951, two of the world's most beloved — and highest paid — movie stars, Katharine Hepburn and Humphrey Bogart, followed director John Huston to a most un-Hollywood location: the sweltering jungle around the Ruki River, in the Belgian Congo (today known as the Democratic Republic of the Congo). There, they spent seven weeks filming a WWI-era romantic-comedy-adventure film about a hard-drinking riverboat captain, Charlie Allnut (Bogart), and his burgeoning love affair with a prim Christian missionary, Rose Sayer (Hepburn).
Photographer Eliot Elisofon was there, too, capturing the stars and crew between takes on the arduous shoot. Here, on the 10th anniversary of Hepburn's June 29, 2003, death at the age of 96, LIFE.com pays tribute to the four-time Best Actress Oscar winner with a series of photos — many of which never ran in LIFE magazine — offering a glimpse inside the making of The African Queen.
The shoot was often a grueling experience for the crew, particularly Hepburn, who suffered from dysentery caused by contaminated water. (She refused to let it affect her work and never missed a day of filming, despite the punishing schedule of what LIFE magazine called "dawn-to-dusk labor.")
For his part, Bogart — like his character, Captain Allnut — liked to drink, and he tossed 'em back throughout the production. (Hepburn later affectionately referred to Bogie and hard-partying director John Huston as "two drunks.") Unlike Hepburn and much of the crew, both Bogart and Huston remained healthy throughout the shoot — probably because they drank far more booze than water.
In the end, the movie proved to be one of Bogart's and Huston's most enduring and fruitful collaborations — which is saying something, considering they worked together on other undisputed classics like Key Largo, The Maltese Falcon and The Treasure of the Sierra Madre. Hepburn received a Best Actress Oscar nomination — her fifth — while Bogart's utterly engaging performance as the cynical drunkard with a heart of gold earned him the only Academy Award of his storied career.
Liz Ronk, who edited this gallery, is the Photo Editor for LIFE.com. Follow her on Twitter @lizabethronk.