Nasdaq and Goldman Sachs are taking the plunge together in the first major “dark pool” deal. Bob Greifeld’s exchange will operate most of Lloyd Blankfein’s “dark” stock trading system, called Sigma X, starting early 2017, in what’s likely to be just the 1^st deal among banks to outsource their technology to Nasdaq.

Sigma X will outsource back-end technology, including compliance and surveillance tools, to Nasdaq’s dark pool operator, called “Ocean,” sources told The Post. That would allow Goldman to bring more trading to its system without having to pay for compliance, sources said. But Goldman will still be on the hook with regulators if something goes wrong.

The final arrangement is not what Greifeld originally envisioned.  In July, he told The Post that Nasdaq was planning “a centralized organization” to farm out banks’ “regulatory burden.” But regulators nixed the idea of Nasdaq operating its own U.S. dark pool, causing the company to change its plans.