The date aligns the two Austrians' contracts with the expiration of the current Commercial Agreement with Formula One Management.
Mercedes motorsport head Wolff, who is effectively the team principal, has a 30 percent stake in Mercedes Grand Prix Limited while non-executive chairman Lauda, a retired triple world champion, has 10 percent.
Daimler AG hold the remaining 60 percent.
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"In 2013, we restructured the management of the Team with the clear goal of improving our performance. Since then, however, the results have exceeded our expectations," said Daimler chairman Dieter Zetsche in a statement.
"A key factor in this success has been the combination of Toto's entrepreneurial skills and Niki's experience. Their renewed commitment gives our programme important continuity for the next four years."
Mercedes have won both the drivers' and constructors' championships for the past three years.
"The last few years have been some of the most enjoyable I have had in Formula One," said Lauda, who won his titles with Ferrari in 1975 and 1977 and McLaren in 1984. He suffered a near-fatal accident in 1976.
(Reporting by Alan Baldwin, editing by Amlan Chakraborty)
