Palin spokeswoman Meghan Stapleton could not be immediately reached to confirm the endorsement.
"Governor Palin is providing tremendous leadership as the Tea Party movement and constitutional conservatives strive to take our country back," Paul said in a statement. "Sarah Palin is a giant in American politics. I am proud to receive her support."
The Paul statement also said that Palin's Political Action Committee had given the Paul campaign a "generous donation."
Paul is seeking the seat now held by Republican Sen. Jim Bunning, who is retiring. A favorite of the Tea Party movement for his support of smaller government and deficit reduction, he is facing off in the Republican primary against Secretary of State Trey Grayson, the GOP establishment pick.
Palin, who has aligned herself with the Tea Party movement, will be headlining a Tea Party convention over the weekend.
In other Palin news, Hotline reports that the former Alaska governor and vice presidential candidate's PAC "spent more money buying copies of Palin's best-selling book than it gave in contributions to political candidates, according to new FEC reports."
Two important notes: The books likely served as a fundraising tool that could be sent out to donors. And while Palin's contributions in the second half of 2009 amounted to just $43,000, it isn't uncommon for PACs to refrain from making significant donations until closer to an election.
Among the politicians to whom Palin has reportedly donated are Reps. Michele Bachmann (R-MN), Marsha Blackburn (R-TN), Roy Blunt (R-MO), Tom Rooney (R-FL) and Jean Schmidt (R-OH), and Sens. Richard Burr (R-NC), Tom Coburn (R-OK), Jim DeMint (R-SC), Lindsey Graham (R-SC), Chuck Grassley (R-IA), Orrin Hatch (R-UT) and John Thune (R-SD).