Yes, The Chinese sailor Zheng He discovered America much before Christopher Columbus did, if one were to go by Gavin Menzies & Liu Gang..
The basis for Liu Gang's claim is a map he picked up for USD 500 in a Shanghai book store in 2001. This 1763 map (with a note about its reproduction from a map dated 1418), presents the world as a globe with all the major continents. Liu Gang, a partner in a well-known Beijing law firm claims to have done extensive research before presenting his findings to public last Monday.
Gavin Menzies, a former British Navy submarine commander, argues in his book 1421: The year China Discovered America that Zheng He visited America in 1421, 71 years before Christopher Columbus did.
If Zheng He did indeed discover America before Columbus did then it topples one of the central tenets for western civilization which states that Europeans discovered America and sailed around the world first.
Unfortunately all this will remain in the relam of speculation only as much of what Zheng He found and discovered have been destroyed by the later Chinese rulers as they went insular and didn't want to connect with the outside world.
NY Times Article - Require registration