Dice the chicken breast into bite-sized pieces and finely chop the onion, carrots, celery, and zucchini.
Heat the olive oil in a medium pot over medium heat, then add the onion, carrots, and celery, sautéing for 5 minutes until softened.
Add the diced chicken, minced garlic, sea salt, black pepper, and dried oregano to the pot, cooking until the chicken is browned on all sides.
Pour in the chicken broth and add the rinsed cannellini beans, bringing the mixture to a gentle boil.
Reduce the heat to low, cover, and simmer for 15 minutes to allow the flavors to meld.
Stir in the zucchini and baby spinach, cooking for an additional 3-5 minutes until the zucchini is tender and the spinach has wilted.
Ladle the hot soup into a bowl and serve immediately.