In a glass or ceramic bowl, combine the chopped shrimp with the lime juice. Make sure the shrimp is completely covered by the lime juice. Cover and refrigerate for about 30 minutes to 1 hour, or until the shrimp is opaque and "cooked" by the acidity of the lime juice.
Drain off most of the lime juice from the shrimp, leaving just a little to keep the ceviche moist.
Add the chopped red onion, diced tomatoes, chopped cilantro, and jalapeño to the shrimp. Mix well to combine.
Season with salt and pepper to taste. Adjust seasoning as needed.
Cover and refrigerate the ceviche for at least 30 minutes to allow the flavors to meld together.
Serve the Mexican shrimp ceviche with tortilla chips or tostadas for scooping up the delicious mixture.
Enjoy!