1919: Germany signs the Treaty of Versailles

Germany signs the Treaty of Versailles, admitting it was responsible for World War I and agreeing to pay reparations.

Footnote: 
I am indebted to Vikash Yadav for this point. (See Weber, Max. “Zum Thema der ‘Kriegsschuld.’”
Year of Apology: 
1919
To: 
France
From: 
Germany