Of the 21, 16 are cardinal electors under 80 years old and thus eligible to enter a conclave to elect his successor after his death or resignation.
After the Aug. 27 ceremony to officially install them, known as a consistory, Francis will have appointed about 83 of the some 133 cardinal electors, increasing the possibility his successor will be a man reflecting his position on key issues.
By then Francis will have appointed about 63% of cardinal electors, further increased their presence in the developing world, and again loosening the grip Europe had on the College of Cardinals.
The new electors include Archbishop Giorgio Marengo, an Italian who is currently the Catholic Church's administrator in Mongolia. The country borders with China, where the Vatican is trying to improve the situation for Catholics.
Other cardinal electors come from France, Nigeria, Brazil, India, the United States, East Timor, Italy, Ghana, Singapore, and Paraguay. Three Vatican officials to be made cardinals in August come from South Korea, Britain and Spain.
Once again, Francis passed over archbishops of major cities that traditionally had cardinals before his election in 2013, preferring to appoint men in far-flung places where the Church is small or growing and more vibrant than in Europe.
By appointing cardinals in Singapore, Mongolia, India and East Timor, Francis appears to be seeking to increase the Church's prestige and clout in Asia, a growing economic and political powerhouse.
New cardinals from other developing countries include archbishops in Ekwulobia in Nigeria, Manaus and Brasilia in Brazil, Goa and Hyderabad in India, Wa in Ghana, and Asuncion in Paraguay.
The promotion to cardinal of Bishop Robert McElroy of San Diego, California, is significant because he has been an outspoken ally of Francis' pastoral approach in issues such as protection of the environment and a more welcoming approach to gay Catholics.
In making McElroy a cardinal, Francis passed over the conservative archbishops of San Francisco and Los Angeles, two large cities that traditionally had cardinals in the past.
(Reporting by Philip Pullella Editing by Emelia Sithole-Matarise and Mark Potter)
By Philip Pullella