Fidelio
Beethoven spent some time working on the opera before he was completely happy with it. The first time it was performed (in 1805) it was a three-act opera called Leonore. There were a lot of French military officers in the audience and they thought they were being criticised.  In 1806 it was performed again with two acts and a new overture (now known as "Overture: Leonore No. 3").  But arguments between Beethoven and the theatre management meant there were no more performances.  Eight years later Beethoven revised his opera again.  This time it was called Fidelio, and it was a great success.  It has remained a famous opera ever since.