The 23-year-old rejoins the Club, having made 10 appearances for the O’s in a loan spell earlier this season, his last appearance coming in the draw against Chester on November 21.
Born in London, Brophy started his youth career at Harrow Town before signing for Broadfields United in 2013.
Following two years at Broadfields, Brophy then joined Edgware Town where he impressed before attracting interest from Swindon Town where he eventually signed during the summer of 2015 after a successful trial.
Having racked up 31 appearances during his debut season at the County Ground, the winger was handed a new deal ahead of the 2016-17 season.
Brophy made a total of 33 appearances for the Robins last season, scoring his first Swindon goal against Queens Park Rangers in August 2016, and has made nine appearances for David Flitcroft’s side this campaign.
Director of Football Martin Ling stated, ‘During his first spell at the Club James impressed us with his professional and conscientious attitude, as well as his ability on the football pitch, which is why we are delighted to have finally brought him back to the Club.
‘I spoke to Justin following his appointment in December and he was very aware of the player and was of the same opinion of myself, Ross Embleton, the coaching staff and the board that he is worth the substantial financial transfer fee.
‘The signing of James looks to conclude our business for this window and we are very pleased with the calibre of players we have brought into this Club.’