The head of state of the host country declares the games open so for London it was the Queen Elizabeth II that opened the 2012 games.
The 1900 Olympics were the first modern Olympic Games to be open to women.
Adolf Hitler
Sydney hosted the Olympic games in Sydney 2000 and it officially opened on the 13th of September and it finished on October the 1st.xx
Olympic Games (Modern) opened in Athens in 1896
Olympic marmot was created in 1898.
Greece Olympic Games Opened 13th Aug. 2004.
Helliniko Olympic Arena is an indoor arena in Greece and was opened on 2003.
Moscow Olympic Arena is an indoor arena in Russia and was opened on 1980.
The O.A.C.A. Olympic Indoor Hall opened in June 1995.
OAKA Olympic Indoor Hall is an indoor arena in Greece and was opened on 1995.
I don't know but it certainly isn'y Barack Obama like somebody answered before
1896 - Athens, Greece The very first modern Olympic Games opened in the first week of April 1896.