This is not exactly the thing that Guinness keeps records on. If you mean male orgasm, well, the typical male orgasm lasts 3-8 seconds. That's pretty much each. With breathing techniques and regular exercise, you can go to 10. However, I don't think that there is any circumstance under which orgasm is elongated. Maybe some rare genetic property, but I can't find anything on this.
It is worth noting that about 1-in-1,250 men can orgasm instantly by their control.
As far as I know the human male orgasm can't go beyond 8 seconds. So I guess noone here will have longer ones. But for me I think the longest as been like 5 seconds although it wasn't during intercourse, don't know if that matters.