Most consecutive bouts fought originally scheduled for the championship distance (either 12 or 15rd)

They don't have to be world title fights per se - as we often see, at least in the modern era, some 12-rounders for lesser trinkets, or world title eliminators, or even in some rare cases simply arbitrarily scheduled for twelve despite there being no tangible prize in the kitty just based on 'star power' (I'm not sure if this was ever true in the 15-round era? 15-rounders generally meant it was a championship fight, unless I'm mistaken?)

Here are the highest numbers tallied up so far:

1. Muhammad Ali - 41 in a row (Liston I through Holmes)
2. Bernard Hopkins - 40 in a row (Aquino through Smith)
3. Roy Jones, Jr. - 36 in a row (Tate through Hopkins II)
4. Manny Pacquiao - 30 in a row (Lucero through Horn)*
5. Floyd Mayweather, Jr. - 26 in a row (Corrales through McGregor)**

*subject to change, but currently penciled in for a match vs. Mike Alvarado in April which as it stands is set to be Pacquiao's first scheduled 10-rounder since Yeshmagambetov in 2003.

**also technically subject to change, if he returns from yet another retirement and immediately challenges for a title (or finagles his way into a 12-rounder by any other means)

A lot of guys I expected to have pretty high #'s, didn't. (SRL, Hagler, Durán, Hearns, Chávez, Robinson et al had just enough 10-rounders sprinkled in at inopportune moments to bust any streaks before they could really bloom...half of these greats, surprisingly, didn't even crack double-digits, and I believe the highest any of the aforementioned got was Hearns with a baker's dozen...just half as many as Mayweather...)

Can we think of any more?

 

Wladimir Klitschko had 22 in a row (Peter I through Joshua).

 

...of Wlad's 22 in a row, twenty-one straight of those were "proper" world title bouts. (he fought 29 world title bouts in all; eight of them prior to Peter I, going 6-2)

...of Ali's 41 in a row, twenty-five were "proper" world title bouts. (Liston I through Folley, then a gap of two fights until Frazier I, then a gap of 14 non-title bouts including the Frazier rematch, then Foreman through Holmes)

...of Hopkins' 40 in a row, thirty-two were "proper" world title bouts, including a stretch of 24 straight (Mercado I through Taylor II) and another of 8 straight (Pascal I through Kovalev)

...of Jones' 36 in a row, twenty-five were "proper" world title bouts, with 5 straight (Tate through Thornton), non-title catchweight affair with Merqui Sosa, then 5 straight (Lucas through Griffin II), non-title affair with Virgil Hill, and then 15 straight (Del Valle through Glen Johnson)

...of Pacquiao's' 30 in a row, fifteen were "proper" world title bouts, with Lucero followed by a non-title featherweight debut in Barrera I, then Márquez I, then eight straight non-title bouts until Márquez II & Diaz, then non-title vs. DLH, fake (IBO) title vs. Hatton, 6 straight "real" world title bouts (Cotto through Bradley I), no world title at stake in Márquez IV or Rios, then 3 straight (Bradley II through Mayweather), Bradley III was non-title, then 2 straight (Vargas, Horn).

...of Mayweather's 26 in a row, twenty were "proper" world title bouts, with 7 straight (Corrales through Ndou), Corley & Bruseles were back-to-back eliminators in a new division, Gatti for a world title belt, then Mitchell was a tuneup in his WW debut, then 4 straight (Judah through Hatton), then Márquez & Mosley were non-title, then 8 straight (Ortiz through Berto).

 

That is absolutely wild.

 

Curiouser and curiouser..."Nutty" Fairhall never actually vied for a recognized world title, despite his entire career being comprised of 15 and 20 rounders!

Held at various points the Aussie light & welter and British Empire lightweight titles, however...

 

People don't really box anywhere near as many rounds, period, these days, let alone in championship fights.