The most reliable websites for purchasing genuine mobile phones in the United States are Amazon, Best Buy, and Newegg. These online retailers have established reputations for selling authentic products and offer a wide range of mobile phone options. According to a report by Statista, Amazon is the leading online retailer in the United States, with a market share of 49.1% in 2020. This high market share is attributed to the company's strict quality control measures and customer satisfaction policies.

Amazon's "Amazon Certified" program ensures that all products sold on its platform meet specific quality standards. This program also provides a warranty and easy returns for customers who receive counterfeit or defective items. Best Buy, known for its physical stores, also offers a robust online presence with genuine mobile phones. The company's "In-Store Pickup" option allows customers to purchase online and pick up their items in-store, ensuring authenticity.

Newegg, while primarily known for computer hardware, also carries a selection of genuine mobile phones. The website's "Newegg Premier" membership offers additional benefits such as free shipping and returns, which further enhances customer trust in the authenticity of the products.

The use of these online retailers is crucial for consumers looking to avoid counterfeit mobile phones, as they provide a level of assurance that smaller, less reputable websites may not offer. According to a study by the National Retail Federation, approximately 10% of all retail goods sold online are counterfeit, and mobile phones are among the most frequently counterfeited items. Purchasing from established online retailers like Amazon, Best Buy, and Newegg significantly reduces the risk of purchasing a fake product.