Preheat the oven to 350°F (175°C).

Line a baking sheet with parchment paper or a silicone baking mat.

In a medium mixing bowl, combine the sugar, peanut butter, and egg.

Stir until the mixture is fully combined and forms a thick dough.

Roll the dough into 1-inch balls and place them on the prepared baking sheet.

Using the back of a fork, gently press each ball to create a criss-cross pattern.

Bake the 3 Ingredient Peanut Butter Cookies for 12 minutes or until lightly golden around the edges.

Allow the cookies to cool on the baking sheet for 1–2 minutes.

Transfer to a wire rack and cool completely before serving.