The name Groß Mahner(Maius Mandere, Magno Mandere) has been used since the end of the 13th century to distinguish it from Klein Mahner to the south-east.

Even today, the centuries-old settlement structure of the district on the eastern side of the Salzgitter ridge can be clearly seen from a bird's eye view: Mahnerstraße, which runs through the village, divides the town into two halves. The northern part is enclosed by the Nordring; the southern part is bordered by the Südring, the southern side of which was only built on in the last quarter of the 20th century.

The Liebenburg office, which once belonged to the territory of the Hildesheim bishopric and to which Groß Mahner belonged, had to be ceded to the Principality of Braunschweig-Wolfenbüttel in 1523 with the end of the Hildesheim Collegiate Feud. While life in the small village, which was dominated by hard agricultural work, probably changed little over the course of time, its political affiliation changed several times in the following centuries: in 1643, the Hildesheim Recess stipulated that a large part of the territories lost in 1523 be returned to Hildesheim, which became Prussian at the beginning of the 19th century.

During the Napoleonic period (1807-1813), Groß Mahner belonged to the department of Oker in the Kingdom of Westphalia, then to the Kingdom of Hanover, which was annexed by Prussia in 1866.

Since April 1, 1942, Groß Mahner has been a district of Salzgitter.

The agricultural village of Groß Mahner experienced an economic boom with the advent of sugar beet in the second half of the 19th century. In 1879, a sugar factory was built a few hundred meters northwest of the town center, which began operations with the 1880 campaign.

The factory, which already produced around 30,000 hundredweights of sugar per year in the early years, was constantly modernized and lasted almost a century before it was closed in the mid-1970s. In August 2004, a major fire on the site of the former sugar factory caused so much damage that the remaining chimneys had to be blown up.

Probably the oldest volunteer fire department in the town with its band founded in 1957, the Mahner Choral Society from 1872 and the Groß Mahner Lawn Sports Club from 1931 are all part of social life in the district, which has a population of around 500.