The following is a list of operas, written in the main western European languages (French, German, Italian, Spanish), which have well-known English titles:
It is proposed that these operas should be listed under their English names with redirects from their original titles. Other operas should be listed under their original titles, with redirects from any known (but not invented) English names.
We hope this will be a practical arrangement that satisfies existing Wikipedia policies, while avoiding too many editorial pitfalls, anomalies and ambiguities.
English names are normally preferred for eastern European, Russian and Scandinavian operas unless the title is a simple proper name. This is for practical reasons.
Here are some examples (with original titles in parentheses):