United National Heavyweight Championship (Zero1)
The United National Heavyweight Championship was a professional wrestling title in the Japanese promotion Pro Wrestling Zero1. It was one of Zero1's top two singles titles, along with the World Heavyweight Championship. The title was created on January 31, 2004 as the NWA United National Heavyweight Championship. Masato Tanaka, then known as Masa Tanaka, defeated Steve Corino in an Indian strap match to become the first champion. It was created at a time when Zero1 was a member of the National Wrestling Alliance ; when Zero1 departed the NWA in late 2004, NWA ceased recognizing or sanctioning it, though it retained the NWA initials. The title was revived by NWA Pro Wrestling in 2011, with NWA beginning to sanction title matches in Zero1 that same year after Zero1 was reinstated as a member of the NWA. NWA stopped sanctioning the title and the NWA initials were dropped after Zero1 left the NWA again later in 2011. In 2020, the championship was retired. There were a total of 26 recognized champions who had a combined 32 official reigns.
Combined reigns
As of,.| Rank | Wrestler | No. of reigns | Combined defenses | Combined days |
| 1 | 1 | 2 | 937 | |
| 2 | 3 | 7 | 458 | |
| 3 | 2 | 8 | 379 | |
| 4 | Towa Iwasaki | 1 | 3 | 314 |
| 5 | 1 | 0 | 313 | |
| 6 | Shogun Okamoto | 1 | 2 | 280 |
| 7 | 1 | 2 | 275 | |
| 8 | 1 | 5 | 258 | |
| 9 | 1 | 1 | 257 | |
| 10 | 1 | 5 | 251 | |
| 11 | 1 | 3 | 250 | |
| 12 | 1 | 2 | 199 | |
| 13 | 1 | 3 | 190 | |
| 14 | 1 | 0 | 182 | |
| 15 | Zeus | 1 | 0 | 170 |
| 16 | Kamikaze | 2 | 2 | 163 |
| 17 | Buffa | 1 | 1 | 133 |
| 18 | 1 | 1 | 117 | |
| 18 | 2 | 1 | 117 | |
| 20 | 1 | 1 | 107 | |
| 21 | 2 | 1 | 106 | |
| 22 | 1 | 0 | 72 | |
| 23 | Sandy Beach | 1 | 0 | 47 |
| 24 | 1 | 0 | 39 | |
| 25 | 1 | 0 | 30 | |
| 26 | 1 | 0 | 26 | |
| 27 | 1 | 0 | 2 |