One World is a manifesto and a travelogue written by Wendell Willkie, a liberal Republican, about his seven-week, 31,000-mile tour.

Originally published in April 1943, it advocates for an end to colonialism, world federalism, and equality for non-whites in the United States.

It is a document of his world travels and meetings with many of the Allies' heads of state as well as ordinary citizens and soldiers in locales such as El Alamein, Russia, and Iran.

Even our relative geographic isolation no longer exists... At the end of the last war, not a single plane had flown across the Atlantic.

[5]Willkie emphasized that across the world the "reservoir of goodwill" towards the United States is much larger than towards other contemporary powers:

I was amazed to discover how keenly the world is aware of the fact that we do not seek—anywhere, in any region—to impose our rule upon others or to exact special privileges ... No other Western nation has such a reservoir.

The editor of Publishers Weekly hailed One World as a 'record-breaking non-fiction best seller,' a phenomenon 'unequaled since the days of the old blue-backed 'speller'—Noah Webster's Revolutionary-era guide to the new American English.

[19] Matthew Rozsa of Salon wrote in 2022 that the book has "an unintentionally humorous subtext" because of Willkie's rumored affair with then-Chinese First Lady Soong Meiling, who was described in the book as having "a generous and understanding heart, a gracious and beautiful manner and appearance, and a burning conviction."