The 2003 Tour Down Under was the fifth edition of the Tour Down Under stage race.

It took place from 21 to 26 January in and around Adelaide, South Australia.

This edition was won by Mikel Astarloza, who rode for AG2R Prévoyance.

[1] 21 January 2003 – Adelaide – Adelaide, 50 km Stage and General Classification after Stage 1 22 January 2003 – Jacobs Creek – Kapunda, 140 km Stage 2 result 23 January 2003 – Glenelg – Hahndorf, 164 km Stage 3 result 24 January 2003 – Unley – Goolwa, 144 km Stage 4 result 25 January 2003 – Willunga – Willunga, 147 km Stage 5 result 26 January 2003 – Adelaide – Adelaide, 90 km Stage 6 result [3]