Ultra-Rare Pokemon Card Hitting Auction Block, Could Fetch $100K!

Wanna add the Holy Grail of Pokemon cards to your childhood collection?

Hope you've got the cash ... TMZ Sports has learned a SUPER rare Trainer card is hitting the auction block -- but it could fetch over $100,000!!!

We're told the No. 1 Trainer promo card is one of the rarest pieces in the history of Pokemon ... with only seven known in existence.

According to the guys over at Heritage Auctions ... the card was handed out to winners of regional Pokemon tournaments as a sort of entry ticket into an exclusive tourney in Tokyo in 1999.

The piece -- graded out as a perfect Gem MT 10 -- features art of Mewtwo and we're told it reads, "The Pokémon Card Game Official Tournament's champion is recognized here, and this honor is praised."

"By presenting this card, you may gain preferential entry into the Secret Super Battle.”

With only seven copies ever created ... we're told the card is even rarer than the legendary Pikachu Illustrator card -- which has sold for over $50K in the past.