The race marked the end of Thomas’ astonishing career.
The 2018 Tour de France champion finished the stage in 62nd position as he rode what became a lap of honour through his hometown.
The final stage began at the velodrome named after the 39-year-old in Newport and went past his childhood cycling club, Maindy Flyers, before ending in Cardiff.
Thomas, who won track gold at two Olympics as well as road race gold at the 2014 Commonwealth Games, is widely regarded as one of the greatest Welsh sportsmen of all time.
“I was emotional crossing the line, I was almost like choking up riding my bike,” said Thomas.
“It’s definitely emotional to finish here and it is just unbelievable really, it is a full circle moment.
Thomas previously said he held discussions over staying on at Team Ineos following his retirement, but that was the last thing on his mind after the race.
“I have got to take the little one to school on Tuesday and then I have my brother’s stag do in Portugal,” joked Thomas when asked about what was next.
“A little bit of normality,” he added.