In a large bowl, combine lime juice, cilantro, garlic, chili powder, cumin, salt, pepper, and olive oil.
Add the chicken thighs to the marinade, ensuring they are well coated. Cover and refrigerate for at least 30 minutes, or up to 4 hours.
Preheat your grill or oven to medium-high heat (about 375°F).
Remove the chicken from the marinade and let excess drip off. Discard the remaining marinade.
Place the chicken thighs skin-side down on the grill or a baking sheet in the oven.
Cook for about 7-10 minutes on the grill or 25-30 minutes in the oven, flipping halfway through for even cooking.
Once cooked, remove from heat and let the chicken rest for 5 minutes before serving.