In a large pot, heat olive oil over medium heat.
Add onion, carrots, and celery. Sauté until softened, about 5 minutes.
Stir in garlic and cook for another minute.
Pour in the chicken broth and bring to a boil.
Add chicken, rice, thyme, salt, and pepper.
Reduce heat, cover, and simmer for about 20 minutes, or until rice is tender.
Stir in lemon juice and garnish with parsley if desired.
Serve hot and enjoy!