Heat the olive oil in a large pot or Dutch oven over medium-high heat. Add the ground beef and chopped onion. Cook, breaking up the meat with a spoon, until the beef is no longer pink and the onion is softened, about 5-7 minutes. Drain off any excess grease.

Add the minced garlic to the pot and cook for another minute until fragrant.

Stir in the taco seasoning and ranch seasoning mix, coating the beef and onions evenly. Cook for 1 minute to toast the spices and deepen their flavor.

Pour in the beef broth, scraping up any browned bits from the bottom of the pot. Add the rinsed black beans, rinsed pinto beans, drained corn, undrained diced tomatoes with green chiles, and tomato sauce.

Stir everything together until well combined. Bring the soup to a boil, then reduce the heat to low, cover, and let it simmer for at least 20 minutes to allow the flavors to meld. For an even deeper flavor, you can simmer for up to an hour.

Ladle the hot taco soup into bowls. Garnish with your favorite toppings like shredded cheese, sour cream, tortilla strips, and fresh cilantro.