Two goals in extra-time earned promotion for Southend after a tense League Two play-off final at the Millennium Stadium.
A disappointing contest of few clear chances appeared to be heading for penalties before Freddy Eastwood smashed home a rebound on 105 minutes.
And five minutes later, Duncan Jupp latched on to Eastwood's pass to slot a low shot into the left corner.
Francis Green's early header was the closest Lincoln came to scoring.
Both teams started nervously, which was no surprise given the prize on offer - and their recent visits to the Millennium Stadium.
Lincoln were hoping to banish the memory of a 5-2 play-off final defeat by Bournemouth two years ago, while Southend have lost the LDV Vans final for the last two years in succession.
Lincoln, with their muscular and direct style, had the better of the opening half.
Very early on, Green threatened with a near-post header but could not quite achieve the desired direction.
Just before the half hour, Mark Bentley did well to hook a clearance under pressure after keeper Darryl Flahavan punched a corner ball into the back of Ben Futcher's head.
After the break, Southend, inspired by Eastwood, began to impose themselves on their opponents.
However, it was the lively Eastwood who wasted a good chance when he missed his kick as the ball broke to him in the box.
Then at the other end, after a pinball passage of play typical of the match, Green blocked Che Wilson's shot with keeper Andy Marriott stranded.
As extra-time approached, Bentley was denied a penalty after Paul Morgan appeared to make contact after the ball had gone.
Southend raised their game in extra-time and pushed forward, while Lincoln seemed ready to settle for spot-kicks.
But Eastwood ensured there would not be a shoot-out when Lincoln's defence could only scramble a header off the line into his path and he volleyed into the back of the net.
Eastwood then turned provider as he released Jupp, who coolly slid his shot beyond Marriott to score his first goal for the club.
Lincoln City: Marriott, McAuley, McCombe, Morgan, Futcher, Sandwith, Butcher, Gain, Green (Beevers 105), Taylor-Fletcher (Bloomer 94), Yeo (Asamoah 90). Subs Not Used: Hanlon, Rayner.
Southend: Flahavan, Jupp, Prior, Barrett, Wilson, Pettefer, Maher, Bentley, Nicolau (Gower 120), Eastwood (Edwards 118), Gray (Dudfield 81). Subs Not Used: Griemink, Guttridge.
Goals: Eastwood 105, Jupp 110.
Ref: M Atkinson (W Yorkshire).