Elversberg will become one of the smallest clubs ever to play in the Bundesliga after securing promotion with a 3-0 win against relegated Preussen Munster.
Goals from Bambase Conte and David Mokwa put Elversberg in control after 15 minutes on Sunday, before Mokwa scored his second midway through the second half to wrap up a second-place finish.
With a population of about 13,000 people, Spiesen-Elversberg will be the smallest town to be represented in the Bundesliga.
Supporters spilled on to the pitch at the 10,000 capacity Waldstadion an der Kaiserlinde at full-time as Elversberg celebrated a remarkable third promotion in the past five years.
Elversberg went close to promotion last season but were defeated 4-3 on aggregate by Heidenheim in the Bundesliga promotion-relegation play-off.
Before that match, rail operator Deutsche Bahn, external posted an image of a train with only one carriage, suggesting that Elversberg would not need a bigger service for the play-off.
The club, founded in 1907 and based in the small state of Saarland in south-west Germany, were playing in the regionalised fourth tier as recently as 2021-22 and until 2023-24 had never played in the second tier.
Their stadium is undergoing renovation in order to meet Bundesliga requirements, with capacity expected to increase to 15,000 by spring 2027.
Elversberg will be joined in the Bundesliga next season by Schalke, who earned the 2. Bundesliga title to return to the top flight after three years away.
The promotion-relegation play-off will be contested by Wolfsburg and Paderborn, who finished 16th in the top flight and third in the second division respectively.