The organelle found within an autotrophic eukaryotic cell that is responsible for photosynthesis is the chloroplast.

Here's why:

* Autotrophic means an organism can produce its own food.

* Eukaryotic cells have membrane-bound organelles.

* Chloroplasts are the sites of photosynthesis, the process where light energy is converted into chemical energy in the form of sugars. This process requires chlorophyll, which is found within chloroplasts.

Let me know if you'd like to know more about chloroplasts or photosynthesis!