Heavyweight Boxing

Robert Fitzsimmons vs Philadelphia Jack O'Brien

A fight that actually happened — and everything both records say about it.

Meetings on record

Robert Fitzsimmons and Philadelphia Jack O'Brien met 2 times (1904, 1905). Philadelphia Jack O'Brien won in 1905 by ko; Robert Fitzsimmons won in 1904.

SOURCE·Bob Fitzsimmons and Philadelphia Jack O'Brien — English Wikipedia (CC BY-SA 4.0)·both records name the other·REVIEWED AUG 2026

How this head-to-head is established

This pairing exists only because at least one of the two articles' own results tables names the other fighter. No matchup on this site is speculative and none is a hypothetical.
Every figure in the comparison below comes from that fighter's own page and carries the same source line. A dash means the source states nothing, not that the value is zero.
Common opponents are found by matching linked bout lists, which is only possible because every fight list here is linked to every other. A shared opponent is not a transitive result and this page does not treat it as one.
Nothing on this page predicts an outcome. It is a comparison of what is on record.

Sources, exclusions and known limits →

Side by side

What both records stateAUG 2026
Robert Fitzsimmons		Philadelphia Jack O'Brien
—	Reach	—
71″ (180.3 cm)	Height	70″ (177.8 cm)
—	Reach advantage	—
69–12	Record	147–16
83%	Finish rate	37%
29	Longest unbeaten run	49
92	Recorded bouts	162
Orthodox	Stance	Orthodox

A comparison of what is on record. Nothing here predicts a result.

Common opponents

Both fought these 5. This is the comparison the siloed databases cannot make, because it needs every fight list linked to every other.

Opponent	Robert Fitzsimmons	Philadelphia Jack O'Brien
Jack Johnson	L	D
Joe Choynski	D	W
Joe Grim	W	W
Peter Maher	W	W
Joe Choynski	D	W

Both records, drawn

The same ledger line on each: wins stamped above the rule, losses below, the mark's shape carrying how it ended.