The winning bidder and a guest will dine with Longoria on the set of her series Desperate Housewives in Los Angeles.
Money generated from the auction will benefit the Variety Foundation, which funds a number of charity groups around the country.
Longoria's lunch date is expected to fetch as much as $5,000 (£3,168).
Bidding is currently under way on the Charity Buzz website.
Last month, Longoria revealed that she would love to direct a feature film in the future.
Desperate Housewives airs Sundays at 9/8c on ABC.
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