This is the Proposed flag of Taiwan favoured by some supporters and activists of the Taiwan Independence Movement.  However, there is no consensus opinion that this flag should be the official representation of Taiwan, in the event that Taiwan should officially declare its independence in the future.
Currently, since Taiwan is a de facto independent state under the official name Republic of China (ROC), the official flag of Republic of China is still commonly used by the majority of Taiwanese people. The Taiwan government as of 2006, even though ruled by the pro-independence Democratic Progressive Party, was still using the official ROC flag (which can be seen at Image:Flag of the Republic of China.svg).

This proposed flag should be used with caution, and only when it is intentional and specific to indicate something related to the Taiwan Independence Movement. For other routinely common usage to represent Taiwan at the present time, use the official flag of Republic of China.
Own work
Originally created by en:user:Mistress Selina Kyle and uploaded to en.wikipedia on January 10, 2006 04.35 under the name Image:Flag of Taiwan.svg (file size 1600x1027 (8518 bytes)). 
Improvements to geometry and layout by user:Reisio

Further improvements to geometry by user:Finlay McWalter - Make the straight edges of the petals tangential to the circular endcaps, avoiding an evident change of gradient at their intersection). Put petals into their own Sodipodi/Inkscape layer.