Essex 169 (Rossington 39, Turner 3-23, Abbott 3-37) and 85 for 4 (Walter 28*, Browne 28, Abbott 3-23) beat Hampshire 120 (Porter 5-37) and 131 (Gubbins 45, Porter 5-46) by six wickets
Jamie Porter claimed 10 wickets for the match for the third time in his career as Essex boosted their LV= Insurance County Championship title hopes while destroying Hampshire's chances.
Quick Porter followed his first-innings 5 for 37 by snaring 5 for 46 in the second innings for match figures of 10 for 83.
It was his first 10-for away from the Cloud County Ground, Chelmsford, first since 2018 and in his renaissance season he now has a Division One-leading 47 wickets.
Chasing 83 to win, Kyle Abbott claimed 3 for 23 but Nick Browne's 28 and Paul Walter's 28 not out took Essex to their sixth win of the season with a six-wicket victory.
Hampshire's gamble to ask for a result pitch backfired as the usual Ageas Bowl seam-friendly pitch which flattens out never flattened out.
That meant almost incessant seam movement, coupled with invariable bounce, made batting tricky - typified by Nick Gubbins' 45 being the highest individual score of the game and only 506 runs coming in total across the four innings.
Hampshire and Essex both knew going into the match that only the winner would realistically be able to challenge Surrey for the title.
Surrey will land on at least 167 points - and more likely 183 - after the conclusion of their clash with Somerset. Essex are now up to 166 points and Hampshire on 135, with 72 points still available.
Hampshire lost their remaining four wickets for nine runs in 25 balls - with Porter and Sam Cook sharing the spoils.
James Fuller's back-foot waft was caught behind to the ninth ball of the day and Abbott lasted four balls before he was brilliantly caught by a one-handed Simon Harmer pounce at second slip.
Porter added Hampshire to Somerset and Worcestershire in his 10-for victims when John Turner drove to Harmer.
Amid the churn of batters, Gubbins was still there having only moved his overnight score from 44 to 45. In seeing No.11 Mohammad Abbas arrive at the crease he aborted his patient style and was bowled attempting to slog across the line with Hampshire all out for 131.
Essex had lost three wickets in their chase of 30 against Kent last week, albeit rushed by incoming rain. They threatened a similar wobble at the Ageas Bowl.
Abbott picked up Alastair Cook nicking behind a drive to the 10th ball of the innings before Tom Westley - the division's second highest run scorer - clipped to midwicket in the fourth over.
But Hampshire's early jubilation was drowned by Browne grafting with Walter - the pair chalking up 33 runs for the third wicket.
Browne was put down at mid off by Liam Dawson before eventually falling lbw to Abbas but the damage he had made through his four boundaries was already fatal to Hampshire's chances.
Matt Critchley had the top of his off stump kissed by a beautiful Abbott in-ducker and Michael Pepper was softly dropped at square leg second ball with 29 still needed. But Pepper and Walter guided Essex to victory in the extra half an hour before lunch.
