Lewis Wickes Hine (September 26, 1874 – November 3, 1940) was an American sociologist and muckraker photographer. His photographs taken during times such as the Progressive Era and the Great Depression captured young children working in harsh conditions, playing a role in bringing about the passage of the first child labor laws in the United States.

Hine was born in Oshkosh, Wisconsin, on September 26, 1874. Following the accidental death of his father, the teenaged Hine was forced to undertake a number of jobs to support his widowed mother and sisters. Aspiring to become an educator like his mother, Hine managed to save a portion of his earnings as the family breadwinner to pay for schooling at the University of Chicago, where he enrolled in 1900. While a student in Chicago, Hine met Frank Manny, a professor of education at the Normal School who was named superintendent of the Ethical Culture School in New York City in 1901. At Manny's invitation, Hine accepted a position as an assistant teacher and relocated to New York. There, he encouraged his students to use photography as an educational medium. Hine also studied sociology at Columbia University and New York University.

Hine led his sociology classes to Ellis Island in New York Harbor, photographing the thousands of immigrants who arrived each day. Between 1904 and 1909, Hine took over 200 plates (photographs) and came to the realization that documentary photography could be employed as a tool for social change and reform.

In 1907, Hine became the staff photographer of the Russell Sage Foundation; he photographed life in the steel-making districts and people of Pittsburgh, Pennsylvania, for the influential sociological study called The Pittsburgh Survey.

In 1908, Hine left his teaching position to become the photographer for the National Child Labor Committee (NCLC). Over the next decade, Hine documented child labor, with a focus on the use of child labor in the Carolina Piedmont, to aid the NCLC's lobbying efforts to end the practice. In 1913, he documented child laborers among cotton mill workers with a series of Francis Galton's composite portraits.

Hine's work for the NCLC was often dangerous. As a photographer, he was frequently threatened with violence or even death by factory police and foremen. At the time, the immorality of child labor was meant to be hidden from the public. Photography was not only prohibited but also posed a serious threat to the industry. To gain entry to the mills, mines and factories, Hine was forced to assume many guises. At times he was a fire inspector, postcard vendor, bible salesman, or even an industrial photographer making a record of factory machinery.

During and after World War I, he photographed American Red Cross relief work in Europe. In the 1920s and early 1930s, Hine made a series of "work portraits", which emphasized the human contribution to modern industry. In 1930, Hine was commissioned to document the construction of the Empire State Building. He photographed the workers in precarious positions while they secured the steel framework of the structure, taking many of the same risks that the workers endured. To obtain the best vantage points, Hine was swung out in a specially designed basket 1,000 ft above Fifth Avenue. At times, he remembered, he hung above the city with nothing below but "a sheer drop of nearly a quarter-mile."

During the Great Depression, Hine, once again, worked for the Red Cross, photographing drought relief in the American South, and for the Tennessee Valley Authority (TVA), documenting life in the mountains of eastern Tennessee.