According to Official Guinness Records,
The longest-running online gaming guild is The Order of the Crimson Cross (USA), which has been in continuous operation for 22 years, 4 months, and 16 days as of 1 March 2018.The Order of the Crimson Cross (www.crimsoncross.org) first appeared in the game Neverwinter Nights hosted by AOL in 1991. The Order began operating consistently in 1995.
For a complete list of 2018 records, please visit 2018 Guinness Records in United States.