There is no credible evidence that Donald Trump announced on Truth Social that he will be suing The Wall Street Journal, NewsCorp, and Rupert Murdoch.
Trump announces on Truth Social that he will be suing: The Wall Street Journal, NewsCorp, and Rupert Murdoch

FactVerify
Source: factverify.com
Key Evidence
Multiple reputable news sources document Trump's criticisms and demands directed at Rupert Murdoch's media properties but do not report any announcement of lawsuits by Trump against The Wall Street Journal, NewsCorp, or Murdoch himself.
thedailybeast.comthedailybeast.comRupert Murdoch-Owned Wall Street Journal Warns Donald Trump Just Put His Own...
the-independent.comthe-independent.comTrump calls for Rupert Murdoch to fire staff at Fox News and the Wall Street...
independent.co.ukindependent.co.ukTrump fumes about Wall Street Journal with Rupert Murdoch right next to him No primary source or direct quote from Trump's Truth Social account confirms such legal action.
What the Evidence Shows
The input claim states that Trump announced on Truth Social his intention to sue The Wall Street Journal, NewsCorp, and Rupert Murdoch. A review of recent news coverage and social media activity shows that while Trump has publicly criticized these entities and called for personnel changes, there is no verified report or direct statement from Trump indicating he plans to file lawsuits against them. The search results reveal multiple instances of Trump expressing frustration and making demands related to Rupert Murdoch's media holdings, including the Wall Street Journal and Fox News, but none mention legal action or lawsuits.
This distinction is important because public criticism or calls for firings are not equivalent to announcing lawsuits. Given the absence of any credible source confirming such an announcement, the claim is unsubstantiated. It is possible that confusion arises from Trump's hostile rhetoric toward these media outlets, but no factual basis supports the specific claim of a lawsuit announcement on Truth Social.