Thirty-two-year-old O`Connor can name Derby County; Doncaster Rovers and Walsall amongst his former clubs and was vice-captain with the Saddlers last season.
Comfortable across the defence, O`Connor has played his entire career to date in the second and third tier, and made forty appearances in League One during the 2016/17 season.
The defender has been training with his new team-mates for the last number of weeks, having left Walsall just over a month ago, and joins Harriers on a deal until the summer of 2020.