| - | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | Y | Z |
| Athlete | Sex | First Appearance | Last Appearance | Appearances | Colleges | Race Types |
|---|---|---|---|---|---|---|
| Uwechue Unchenna | m | 2012-02-04 | 2012-04-21 | 3 | IT Sligo | 800m |
| Benjamin H.T. "Ben" Underwood | m | 1968-05-01 | 1971-05-12 | 9 | TCD | 100y, 200m, 220y, 4x100m, 4x110y |
| J.P. Unger | m | 1929-07-03 | 1929-07-03 | 1 | Atalanta | DT |
| Des Unknown | m | 1996-11-23 | 1996-11-23 | 1 | TCD | Road |
| Raja Unknown | m | 1996-11-23 | 1996-11-23 | 1 | TCD | Road |
| Stan Unknown | m | 1996-11-23 | 1996-11-23 | 1 | TCD | Road |
| Barry Upton | m | 2004-12-03 | 2012-04-21 | 37 | IUAA, WIT | 16kgWfD, 200m, 400m, 400mH, 4x100m, 4x200m, 4x400m, 60mH, SP |
| Samuel Urvoy | m | 2004-12-03 | 2004-12-04 | 1 | UL | 60m |
| Karl Ussher | m | 2000-12-01 | 2000-12-02 | 3 | UCD | 60m, LJ |
| Uchenna Uwechue | m | 2012-11-17 | 2013-03-09 | 4 | DCU | 1500m, Road, XC |
| Pamela Uddin | f | 2011-03-12 | 2011-03-12 | 1 | WIT | XC |
| Eva Unknown | f | 1996-11-23 | 1996-11-23 | 1 | TCD | Road |