In the mouth.
Ingestion is the process by which food is taken inside the body of an organism. Different animals ingest food in different ways.There is no specific organ where ingestion takes place.
In most multicellular organisms, ingestion takes place from mouth.
In unicellular organisms, there are special structures in each organism for ingesting procured food.
AMOEBA uses protoplasmic extensions called pseudopodia which engulf the food.
PARAMECIUM has short hair like structures on the body called cilia, which sweep food particles from the water.
BUTTERFLY has feeding tube to suck nectar from flowers.