Leucojum vernum, called spring snowflake.

The spring snowflake is native to central and southern Europe from Belgium to Ukraine. It is considered naturalized in north-western Europe, including Great Britain and parts of Scandinavia, and in the US states of Georgia and Florida. It is cultivated as a spring-flowering ornamental bulbous plant. Usually a single white flower with greenish marks near the tip of each tepal is borne on a stem about 10–20 cm tall, occasionally more. Photo taken in the Westpark of Munich.