Greta Van Susteren is out at MSNBC after just six months. The Post has learned that she’ll be replaced by Ari Melber, MSNBC’s chief legal correspondent.

Van Susteren, who moved from Fox News to the left-leaning network in January, tweeted on Thursday afternoon, “I am out at MSNBC.”

In an internal memo obtained by The Post, MSNBC president Phil Griffin told staff, “As we continue to grow and evolve as a network during one of the most newsworthy periods in recent history I have important news about our 6pm hour. MSNBC and Greta Van Susteren have decided to part ways.”

Griffin added, “I’m also pleased to share that Ari Melber, MSNBC’s Chief Legal Correspondent and host of the ‘The Point’ on weekends will become the permanent host of the 6pm hour next month. Ari is a frequent presence on TODAY and across various MSNBC shows and will continue those appearances as he takes on his new duties.”

Van Susteren is not expected to return to the air. Griffin said there would be a “rotation” of hosts until Melber takes the chair.