Indian conglomerate Tata ceased production at its Dalzell steel plate mill in Motherwell and the Clydebridge plant in Cambuslang in 2015 with the loss of 270 jobs.
The plants were subsequently bought by metals firm Liberty House earlier this year, and the First Minister will officially mark the restart of the Dalzell steel.
Sturgeon said the reopening is a "very positive signal that the steel and engineering industries still have a future here in Scotland."
Liberty House said many of the 120 staff at the plant are former employees, and it hopes to increase employment to 200 within 18 months.
Dalzell is the last major steelworks in Scotland and has provided steel plate used in industries such as shipbuilding, construction, mining, oil production and heavy vehicle manufacture.
The owners said the plant has "already secured a significant number of orders for plate", particularly in the construction and energy sectors, and they expect the revamped plant to be worth around £15m a year to the economy.
Scottish ministers played a key role in the deal through a ''back to back'' agreement involving the Government buying the plants from Tata and immediately selling them on to Liberty, with the sale completed under the same terms with no cost to the taxpayer.
Liberty House Group executive chairman Sanjeev Gupta said: "There is an impressive spirit of partnership here and a determination to give the Scottish steel industry a real future. From our side we promised we would get this important plant open again by the autumn and today we are proud to be fulfilling that promise."
He said the firm sees "great opportunities for investment in Scotland and regard this as a very fertile business environment", adding that the neighbouring Clydebridge works will reopen when market conditions allow.
Jon Bolton, chief executive of Liberty Steel UK Plates and UK Steel Development, said: "Restarting this mill only nine months after production was halted has been a tremendous achievement.
"Seeing the plant producing steel plate once again is just reward for all the determination and hard work of the team here at Dalzell. We now intend to ramp production up as quickly as the market will allow."
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