From 2000 to 2016 China increased its scientific publications in the international journals indexed by Scopus to become the largest contributor to global science, accounting for about 23% of journal articles adjusted for the Chinese share of addresses or names on publications. Publications with all-China addresses contributed the most to the increase, followed by cross-country collaborations and papers by Chinese-named researchers outside the country. The same period also saw a huge increase in scientific publications in Chinese language journals not indexed in Scopus. We estimate that while Chinese language papers gain about 1/5th as many citations as non-Chinese (largely English) papers in Scopus they are so numerous that even valued as making 1/5th the contribution of a Scopus paper, China accounts for 36% of global scientific papers defined as Scopus papers and China language equivalent papers and for 37% of citations to those papers. China's move to the forefront of scientific inquiry makes it a key driver of the direction of scientific and technological progress and of the knowledge-based economies of the foreseeable future.