Make the chimichurri: In a blender or food processor, combine the parsley, cilantro, garlic, red wine vinegar, olive oil, and red pepper flakes. Blend until well combined but still slightly chunky. Season with salt and pepper.
Pat the shrimp dry with paper towels and season generously with salt and pepper.
Heat a grill pan or regular pan over medium-high heat. Cook the shrimp for 2-3 minutes per side until pink and cooked through.
Remove the hot shrimp from the pan and immediately toss with the chimichurri sauce while still warm.
