Smyth's debut goal earns Northern Ireland victory over South Korea
There were just six minutes left until the end of the friendly match when the 20-year-old Queens Park Rangers forward was sent on by Northern Ireland manager Michael O'Neill and it took him just two minutes to score.
Conor Washington overpowered a defender and Smyth got on the ball before cutting inside and then producing a composed finish that gave South Korea goalkeeper Kim Seung-Gyu no chance, to the delight of the Windsor Park faithful.
South Korea had dominated much of the second half but, significantly, were unable to add to their tally after the opening 45 minutes ended all square at 1-1, with an early Kwon Chang-Hoon strike cancelled out by an own-goal from Kim Min-Jae.
Unlike South Korea, Northern Ireland won't be heading to Russia 2018 after a controversial penalty led to a goal that saw them beaten 1-0 by Switzerland in a two-legged play-off.
O'Neill, who turned down an approach from Scotland to stay on as Northern Ireland manager, gave international debuts to Motherwell goalkeeper Trevor Carson and Norwich full-back Jamal Lewis.
South Korea fielded both of their Premier League stars -- Tottenham Hotspur forward Son Heung-Min and Swansea midfielder Ki Sung-Yeung -- from the start.
It took the visitors just seven minutes to open the scoring.
Park Joo-Ho undid the home defence with a ball over the top and Kwon Chang-Hoon, coming in off the wing, took one touch for control before shooting past Carson.
Northern Ireland, however, were back on level terms in the 21st minute.
From a 25-yard free-kick, Oliver Norwood, instead of shooting at goal, slid a pass round the side of the wall to Jamie Ward, whose hard-hit cross was turned into his own net by defender Kim Min-Jae.
South Korea went close to a second goal in the 57th minute when a diving Carson saved well after Park's shot was deflected off Kwon.
As often happens in friendlies, a raft of substitutions around the hour led to a disjointed game.
Son, to the undoubted relief of Spurs boss Mauricio Pochettino, was substituted 15 minutes from time in what appeared to be a purely tactical, rather than injury-induced, change.
For Northern Ireland, Smyth, who plays his club football in England's second-tier Championship, came on to win his first cap and then crowned an already memorable day with a well-taken goal.