Ron Paul of Texas suspended his active campaign operation in May but said he would still pursue delegates so he could have some influence during the Republican National Convention in Tampa, Fla., in August.
"My first choice had always been my father. I campaigned for him when I was 11 years old. He's still my first pick," Rand Paul told Fox News Thursday. "But now that the nominating process is over ... I'm happy to announce that I'm going to be supporting Governor Mitt Romney."
In a statement posted on his Web site, Romney said he was honored to have the Kentucky senator's backing.
"Senator Paul has been a leading voice in the effort to scale back the size and reach of government and promote liberty. … I am grateful for Senator Paul's support and look forward to working with him to get America back on the right track," the presumptive Republican presidential nominee said.
Romney has more than the 1,144 delegates necessary to win the party's presidential nomination. The last state conducting a Republican primary is Utah, which holds its party primaries June 26.