I don't believe it's a MIL Spec circular connector as both Andre and Yura have suggested.
It looks like a DIN/mini-DIN variant which are typically available in up to 20 conductors.
It would be helpful to see the mating side and something for scale.
In any event you should brace yourself, whether it is a MIL Spec Circular connector or a high density mini-DIN, both are quite expensive.
They can typically range in price from $75 to several hundred dollars a unit.
Most of the high density mini-DINs are available with prewired pigtails, typically in the $125 to $200 range.
BigDog