The 20-year-old will spend the rest of the season with the Robins after a strong start to 21/22 with Palace’s Under-23s.
O’Brien has played 14 games for Paddy McCarthy’s side this season, helping the young Eagles sit sixth in their first Premier League 2 campaign.
Swindon are having a similarly strong season, sitting fifth in League Two. They are just three points off an automatic promotion place to return to the third tier.
Commenting on the move, O’Brien said: “I’m delighted to have earned this loan to Swindon at such a pivotal time in their season. I’d like to thank both Palace and Swindon, and look forward to learning from the manager and his coaches.”