Israel returned the Sinai peninsula to Egypt 1982 after a gradual withdrawal as part of the 1979 peace treaty.

If you count it, the Russian de-facto annexation of South Ossetia and Abkhazia.

Armenia still occupies parts of Azerbaijan since the 1994 cease fire in the Nagorno-Karabakh war.

Britain peacefully transferred Hong Kong to China 1997. Likewise, Portugal handed over Macau to the Chinese in 1999.

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, you may PM /u/caffarelli to have your question considered for an upcoming Tuesday Trivia thread.