The Treaty of Versailles ended World War I and is often considered the reason World War II would occur.
The treaty included many significant aspects including:
The 'war guilt' clause which Germany had to accept all charges and accountability for the war.
Reparations to be paid by mostly by Germany (this comes with their acceptance of the 'war guilt' clause)
A demilitarized zone between France and Germany called the Rhineland
Loss of colonies by the Triple Alliance (particular harmful for Germany)
Reduction of German military forces
Creation of the League of Nations