Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Add the mashed ripe bananas to the butter and sugar mixture and mix until combined.
Beat in the egg and vanilla extract until fully incorporated.
In a separate bowl, whisk together the all-purpose flour, baking soda, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet banana mixture, stirring just until combined. Do not overmix.
Fold in the semi-sweet chocolate chips evenly throughout the dough.
Using a tablespoon or cookie scoop, drop rounded spoonfuls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden and the centers are set but still soft.
Remove the cookies from the oven and allow them to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.