Monday, September 18, is National Cheeseburger Day. As you’d guess, restaurants all over the country are celebrating the event with special deals and discounts on cheeseburgers.

McDonald’s and Burger King aren’t participating (at least not on a national level), but many other burger chains have great promotions. There are free cheeseburger upgrades, cheeseburger eating challenges, special cheeseburger promotional pricing—and yes, some offers for totally free cheeseburgers. Here are the deals you need to know about, valid at participating restaurants only.

Applebee’s: Burgers that normally cost in the neighborhood of $9 to $12 are being priced at a flat $6.99 on Monday.

BurgerFi: The BurgerFi Cheeseburger—a double with angus beef and American cheese that normally costs about $7—is available at the special price of $5 on Monday. Just mention the offer at the register, and note there is a limit of one $5 burger per customer.

Dog Haus: All customers can upgrade from a single to a double cheeseburger at no extra charge on National Cheeseburger Day.

Fuddrucker’s: Are you up to the 3-Pound Burger Challenge? On Monday, Fuddrucker’s is daring customers to order a 3-lb. burger with a 1-lb. order of fries and endless Coca-Cola beverages for $24.99. If you finish the entire order in one hour, you’ll get a $20 gift card and a T-shirt proclaiming your accomplishment.

Hwy 55: From 5 p.m. until closing on Monday, Lil’ Cheeseburgers at Hwy 55 are just 55 cents apiece (normal price: $3.39). Each Lil’ Cheeseburger can be accompanied with up to 13 toppings, including lettuce, tomato, onion, chili, and grilled mushrooms.

Ninety-Nine Restaurant & Pub: Cheeseburgers with your choice of American, Swiss, or cheddar cheese are $5 each on National Cheeseburger Day.

Shake Shack: From 11 a.m. to 2 p.m. on Monday, Shack Burgers are free when ordered and delivered by DoorDash. Enter the promo code SHACK at checkout.

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