Butter a 9x13-inch baking dish.
Combine sugar, butter, and evaporated milk in a medium saucepan over medium-high heat; cook and stir until mixture comes to a boil.
Boil for 4 minutes, stirring constantly.
Reduce heat to low.
Stir in marshmallow cream until melted.
Stir in peanut butter until combined.
Pour fudge mixture into the prepared baking dish.
Cool at room temperature before cutting into squares, at least 30 minutes.
