The winger struck midway through the second half, thumping in just a second goal in the past eight matches for Mark Molesley’s side, to earn only a fourth away win of the season and close to within three points of safety with eight matches left to play.
Mid-table Harrogate edged the chances in a scrappy encounter in North Yorkshire, but the crossbar denied Brendan Kiernan in their closest opportunity.
Story of the match
With time running out to launch their escape from the drop, Southend were in greatest need of the points and started with some promising touches. Nathaniel-George had James Belshaw at full stretch to deny one effort from outside the box and the goalkeeper also had to field an Emile Acquah shot, but otherwise there would be minimal first-half threat from the EFL’s lowest scorers.
Instead it was the hosts who offered the greater promise of a goal. Mark Oxley was forced into an excellent reaction save to deny Simon Power on the counter, before Aaron Martin scrambled the ball in from a George Thomson free-kick only for the offside flag to be raised before any celebrations could begin.
Oxley was soon required again, making a fine double save to first deny Josh McPake following a mazy run, and then Jack Muldoon with the rebound as well. Skipper Josh Falkingham glanced a Power cross over as Harrogate began to accumulate chances, the final one before the break seeing Oxley make up for failing to clear a ball by denying Connor Hall.
Despite the loss of their captain, John White, at the interval through injury, Southend re-emerged a more dangerous side, and only a confident block by Belshaw denied Simeon Akinola from breaking the deadlock after a mistake at the back.
Nathan Ferguson and Acquah missed further chances before Harrogate came closest of all, when Muldoon pulled the ball back from the byline and substitute Kiernan stabbed against the frame of the goal.
Just as the hosts looked on top once more, an incisive counter caught them out. Akinola found Alan McCormack and the midfielder beat Belshaw, only for Hall to block on the line. The chance was not gone though, as Acquah won the battle with Will Smith for the second ball, allowing Nathaniel-George to thump home a vital goal.
Harrogate pushed forward in search of a leveller but, unlike their last away trip to Scunthorpe United, Southend were not to be denied at the death this time around, Muldoon firing a whisker wide of the post in the best late chance.
Blues find sufficient spark
No side in the EFL have found goals harder to come by this season, and a run of just one goal in the past seven matches had left Southend looking like not only dropping out of the League after 101 years, but doing so with little more than a whimper.
The only goal they had scored in that run came from Nathaniel-George in the trip to Scunthorpe last weekend, but a 90th-minute leveller saw crucial points slip from their grasp and the situation looked more dire than ever.
The winger was the brightest spark for them here and again found the net, but the effort was also aided by the contributions of Acquah, Akinola and James Olayinka, who all looked bright and hungry to give their attack a more promising edge.
And crucially, the lead did not slip this time. They are still in the fight of their lives with only eight games remaining to claw their way out of trouble, but for Southend this is not just the result, but the performance as well, which suggests they still have every chance.
Sulphurites edged out again
Mid-table safety represents a more than impressive first campaign in the EFL for Harrogate, but it also means that their season is fizzling out, nine points from the play-offs and 13 from the bottom two.
This performance did little to dispel that feeling, with the usual battling qualities present in abundance but a certain spark more evidently lacking. Muldoon looked to make things happen and Power’s first-half injury weakened them, but beyond a brief spell following the introduction of Kiernan there was not too much to excite.
Goals are usually a rare commodity in Harrogate matches, especially at their EnviroVent Stadium home, and this is the 15th league match this season that has finished 1-0, representing close to half of all their games.
This was their eighth defeat by that scoreline, with seven wins on the flipside, and turning more of these close duels in their favour – or even into draws, with no team in League Two sharing the spoils fewer times this season – will give them a chance of pushing on further next year.
Man of the match - Ashley Nathaniel-George (Southend)
The most dangerous player throughout the match for Southend, and his decisive goal was fully deserved for all his endeavour.