Heat olive oil in a large pot over medium heat. Add onion, carrots, and celery and cook until softened, about 5-7 minutes.
Add garlic, cumin, paprika, and thyme and cook for 1 minute more.
Pour in vegetable broth and add lentils and diced tomatoes. Bring to a boil, then reduce heat and simmer for 20-25 minutes, or until lentils are tender.
Stir in spinach and cook until wilted, about 2 minutes. Season with salt and pepper to taste.