"Bachelorette" contestant Erich Schwer -- the last remaining candidate for Gabby Windey -- is owning up to wearing blackface as part of a Halloween costume in high school ... saying he deeply regrets his actions.
A photo from Schwer's old yearbook made rounds on social media this week ... showing him dressed as Jimi Hendrix, donning dark makeup and an afro wig.
The 29-year-old real estate analyst from New Jersey is now speaking out on his costume choice ... saying he wholeheartedly apologizes for what he thought was a gesture showing love for the artist, but admits it only showed ignorance.
"I am deeply ashamed by my actions and understand that my apology is only the first step in taking accountability."
Schwer is Gabby's final chance at love on this season of the dating show ... after she parted ways with Johnny and Jason during the Fantasy Suite episode.
It's not the first controversy involving race for the franchise -- "Bachelor" contestant Rachel Kirkconnell was criticized for attending an antebellum plantation-themed event in college ... and later admitted she was wrong.