The “best” diamond company can be subjective and may depend on different things, such as your specific needs, budget, and preferences. There are many well-known and reputable diamond companies in the industry, each with its strengths and areas of expertise. Here are some of the most respected and recognized diamond companies:

1. De Beers: De Beers is one of the world’s largest and most influential diamond mining and trading companies. It has a long history in the diamond industry and is known for its role in shaping the diamond market.
2. Tiffany & Co.: Tiffany & Co. is a renowned luxury jewelry brand known for its high-quality diamonds and iconic blue box. They are known for their exceptional craftsmanship and timeless designs.
3. Graff Diamonds: Graff is famous for dealing with some of the world’s most exceptional and rare diamonds. Their creations often feature large, high-quality diamonds in exquisite settings.
4. Harry Winston: Harry Winston is a respected jewelry brand known for its exceptional diamonds, including rare-colored diamonds. They have a history of acquiring some of the world’s most famous diamonds.
5. Cartier: Cartier is a prestigious French jewelry brand with a reputation for high-quality diamonds and elegant designs. They offer a range of diamond jewelry, including engagement rings.
6. Blue Nile: Blue Nile is a well-known online diamond and jewelry retailer. They offer a vast selection of diamonds and engagement rings at competitive prices.
7. James Allen: James Allen is another famous online diamond and engagement ring retailer. They are known for their high-resolution 360-degree diamond viewing technology and customization options.
8. Brian Gavin Diamonds: Brian Gavin is known for its expertise in diamond cutting and precision craftsmanship. They offer a selection of well-cut diamonds with excellent light performance.
9. Whiteflash: Whiteflash is recognized for its high-quality diamonds, particularly its A CUT ABOVE® line of super-ideal cut diamonds known for exceptional sparkle and brilliance.
10. Ritani: Ritani is a jewelry brand offering online and in-store shopping options. They provide a selection of diamonds and customizable engagement rings.

When picking out a diamond company, consider your specific requirements, such as budget, desired diamond quality, and whether you prefer to shop in-store or online. Additionally, ensure the company adheres to ethical and responsible sourcing practices and provides reputable diamond certifications from recognized gemological laboratories. Ultimately, the best diamond company for you will align with your individual needs and preferences.