Yes, you can use your cellphone in Hawaii. Hawaii is part of the United States, so if you have a mobile phone plan with a U.S. carrier, you should have coverage in Hawaii without any additional fees or roaming charges.
If you are traveling from outside of the United States, you should check with your mobile phone provider to ensure that your phone will work in Hawaii and to find out about any additional fees or roaming charges that may apply.
Keep in mind that if you plan to use your cellphone for navigation or other data-dependent activities while in Hawaii, it’s a good idea to check your data plan to avoid unexpected charges. Additionally, some areas of Hawaii may have limited cellular coverage, particularly in more remote areas, so it’s a good idea to have a backup plan for communication in case of emergencies.