The Pakistan bowler recorded figures of 8 for 17 off 11.5 overs as Sussex tumbled to 54 all out in just 98 minutes in reply to Glamorgan's 172 on the second day of the County Championship match. Waqar's previous personal best was 7 for 25 - set only last Saturday against Lancashire at Liverpool.
This was an even better performance and easily eclipsed Kevan James' hold on the best bowling performance of the season of 8 for 49 for Hampshire against Somerset at Basingstoke earlier this month.
Swinging the ball both ways in the air and getting movement off the pitch, Waqar was in awesome form. The ball which dismissed Neil Taylor - a lifter that left him desperately late and was touched to wicketkeeper Adrian Shaw - would have got the better of any batsman.
Twice he took two wickets in three balls and he was also indebted to some good work by Robert Croft at third slip, who caught Keith Greenfield, Peter Moores and Vasbert Drakes.
But Waqar needed no assistance with the other four and his last two spells for Glamorgan have produced remarkable figures of 18.5-5-42-15.
Earlier, James Kirtley had also finished with career-best figures of 6 for 60 as Sussex mopped up the remaining Glamorgan resistance in just over 90 minutes.
Resuming at 114 for five, Glamorgan were dismissed for 172 with Kirtley taking three more wickets to add to the three he claimed on Thursday.
It was Mark Robinson who broke the overnight partnership of Robert Croft and Adrian Shaw, having Croft caught by Bill Athey at second slip for 24 before Kirtley took over.
The 22-year-old right-arm seamer held a good return catch one handed above his head to send back Waqar Younis and then bowled Darren Thomas before he had scored.
Shaw and Steve Watkin then frustrated Sussex with a ninth- wicket stand of 31 in 13 overs.