In a mixing bowl, combine the graham cracker crumbs, melted butter, and granulated sugar. Mix until well combined and crumbly. Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish. Set aside.

In a separate bowl, whisk together the sweetened condensed milk, lime juice, and lime zest until smooth.

In another mixing bowl, beat the heavy cream until stiff peaks form. Gently fold the whipped cream into the lime filling mixture until everything is well incorporated.

Pour the lime filling into the prepared graham cracker crust, spreading it evenly.

Cover the pie with plastic wrap and refrigerate for at least 4 hours, or until set.

Before serving, garnish with fresh lime slices if desired. Slice into pieces and enjoy!