Lynch blasted home from the edge of the penalty area with what proved the game’s decisive goal at Inver Park on 86 minutes.
It secured three superb points for Larne to push Tiernan Lynch’s side back into fourth spot in the Premiership standings - with the visitors’ 2-1 loss leaving the league leaders’ lead over Linfield at three.
Lynch was the second substitute on the scoresheet following a Glentoran equaliser thanks to Ruaidhri Donnelly’s stooping header.
That goal served to cancel out a Lee Bonis effort that kicked off the second half in style.
Play before the break proved competitive with sights of goal limited.
The first half almost finished with a goal, however, on 43 minutes when Ben Doherty’s whipped cross was met by Bonis at the back post but his header hit the crossbar.
The combination led to scoring success in the second half as Doherty sent a cross into the danger zone and Bonis was aggressive to challenge Patrick McClean and force home the ball.
It marked a sixth goal in nine games for the January signing by Larne from Portadown for £100,000.
Larne attempted to take advantage of the upper hand but Mark Randall’s drive from distance cleared the crossbar.
The Glens’ triple substitution on 72 minutes was designed to increase the attacking options - and Donnelly made his mark by moving low to flick home Conor McMenamin’s ball into the box.
Jeff Hughes had earlier hit the crossbar for Larne and a third attempt on the night off the woodwork arrived when the hosts’ John Herron was denied by the frame of the target.
However, the game’s final goal handed Larne control when fellow substitute Andrew Scott found Lynch and his slick strike proved beyond Aaron McCarey.
McCarey then produced a string of last-gasp saves at 2-1 to prevent Scott and Lynch from increasing the vital lead - but, ultimately, the one-goal gap proved enough for home delight over Glentoran.
Larne: Devlin, Balmer, Watson, Sule, Herron, Randall, McDaid, Doherty, Bolger, Bonis, Hughes.
Subs: Ferguson, Kelly, Nasseri, Hale, Scott, Lynch, Jarvis
Glentoran: McCarey, Kane, Marshall, J.Donnelly, McDaid, Murray, McClean, Clucas, Marron, McMenamin, Plum.
Subs: Garrett, Burns, McCartan, R.Donnelly, O’Connor, Cushnie, Glendinning
referee: Tony Clarke
A message from the Editor:
Thank you for reading this story on our website. While I have your attention, I also have an important request to make of you.
In order for us to continue to provide high quality and trusted local news on this free-to-read site, I am asking you to also please purchase a copy of our newspaper whenever you are able to do so.
Our journalists are highly trained and our content is independently regulated by IPSO to some of the most rigorous standards in the world.
But being your eyes and ears comes at a price. So we need your support more than ever to buy our newspapers during this crisis.
With the coronavirus lockdown having a major impact on many of our local valued advertisers - and consequently the advertising that we receive - we are more reliant than ever on you helping us to provide you with news and information by buying a copy of our newspaper when you can safely.
You can also enjoy unlimited access to the best news from across Northern Ireland and the UK by subscribing to newsletter.co.uk
With a digital subscription, you can read more than five articles, see fewer ads, enjoy faster load times, and get access to exclusive newsletters and content. Visit https://www.newsletter.co.uk/subscriptions now to sign up.