Putin on Tuesday is set to unveil a 19-kilometre-long bridge linking southern Russia to the Crimean peninsula annexed from Ukraine.
Known as the Crimean Bridge, at nearly 12 miles it will be the longest not only in the country but also in Europe, overtaking the Vasco da Gama Bridge in Lisbon.
Built at a cost of 228 billion rubles ($3.69 billion), the new structure connects the southern Krasnodar region with the Crimean city of Kerch, spanning a strait between the Black Sea and the Azov Sea.
Ukraine has condemned the project saying construction has damaged the environment and that larger ships will be unable to get through to its ports on the Azov Sea.
European Union and US sanctions have targeted those involved in the bridge, principally Putin's close ally, businessman Arkady Rotenberg, whose company Stroygazmontazh won the construction contract.
The annexation of the peninsula in 2014 was condemned by Kiev and the West as an illegal land grab but applauded in Russia.
Currently the peninsula is hard to reach from southern Russia as there are often long queues of vehicles trying to board ferries, which cannot always run in winter storms, so the easiest way across is to fly.
Due to the blocks imposed by Kiev and Western sanctions, a large amount of food is currently transported to the peninsula from Russia by ship, meaning the bridge will play an important role in reducing the region's reliance on sea transport.
Crimea is popular among Russians as a summer holiday destination and Putin said in March he would like the bridge to be ready for the season.
Such a bridge was first proposed under the last Tsar Nicholas II before World War I broke out, preventing it going ahead.
Another unsuccessful attempt was made in the 1930s under Joseph Stalin. During World War II the occupying Nazis also began building a bridge, but this is the first time it has been completed.
Putin highlighted the achievement when he visited the site in March and hailed the "mighty" bridge.
"This is a project that they tried to achieve back under the tsar.. Then in the 1930s they tried to do it -- they also couldn't. And they tried later -- nothing worked out. But we managed it. That's great," he told hard-hatted workers.
He called the bridge "just a unique structure not just for our country but I think that in the whole world there are few similar."
The road bridge is opening ahead of schedule as it was due to be completed in December. When opened for traffic on Wednesday, it will be able to carry up to 40,000 cars per day on four lanes.
The railway bridge is not yet finished and has a deadline of the end of 2019. A connecting highway from Kerch to the regional capital of Simferopol will only be completed in 2020.
Ships will be able to pass through an arch of the bridge that is 35 metres high in the deepest part of the strait. It is also designed to withstand ice floes in winter.
The construction is one of Putin's legacy projects, after the massive renovation of the Black Sea city of Sochi for the 2014 Winter Olympics and the 2012 opening of the world's longest cable-stayed bridge in the far eastern city of Vladivostok.
Russians overwhelmingly voted for Putin to serve a fourth Kremlin term in March but an opinion poll by the independent Levada centre found 45 percent of the population thought he was failing to ensure the country's oil and gas revenues trickled down to benefit ordinary people.
Nevertheless, a Levada poll in March found 70 percent of Russians thought taking Crimea had been beneficial.