I won a prize valued at $12,500. What are the tax implications

[skintzel]

The prize included the $10,000 entry fee into a WPT Poker tournament. If I did not win anything in the poker tournament, can I claim the $10,000 entry fee as a gambling loss to offset the value of the prize. The entry fee was paid directly to the casino but I have my registration form for the tournament which lists the entry fee.

[DanielV01]

In this case, unless you are a professional gambler, you would claim the $12,500 as gambling winnings, and the $10,000 entry fee would qualify as gambling loss.  Be advised, however, that the gambling loss may not offset the winnings entirely (or possibly not at all).  In order to be deductible you must be able to itemize deductions on your return, which means your itemized deductions must be more than $12,000 if you are filing single and $24,000 if you are filing married.  

Normally a prize would be considered as miscellaneous income, for which deductions are no longer allowed.  But your winnings are directly tied to gambling, so they are correctly treated as gambling winnings.