https://www.inverse.com/article/53182-the-expanse-season-4-amazon-release-date-trailer-plot-cast-and-more

JUNE 2019 according to the above link.... **

** While there’s no official release date scheduled yet, Deadline reported in late January 2019 that The Expanse Season 4 would release sometime in 2019.

However, we can make some guesses about when it might actually air.

Production on Season 3 ran from July 12, 2017 to December 6, 2017, and then it aired weekly from April to June 2018. That’s four months between production’s end and the first episode airing.

We also know that production on Season 4 ended on or around February 8 and a pre-emptive wrap party for the season was held in late January. If production to air dates remain the same, then we could be looking at a June 2019 release date at the earliest.

It’s also possible, however, that because The Expanse is an Amazon show now, the entirety of Season 4 — supposedly 10 episodes in total — will release all at once. If that is indeed the case, then the time between the end of production and the series air date is closer to six months. So Season 4 might not be released on Amazon until July 2019.

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