Jensen and Danneel announced on Thursday night (6 June) that they had welcomed daughter Justice Jay "JJ" Ackles on 30 May.
Danneel tweeted: "We are happy to announce the birth of our precious baby girl. She was born happy and healthy on May 30th."
Jensen, who plays Dean Winchester in Supernatural, and Danneel, who played Rachel on One Tree Hill, married in Dallas, Texas in May 2010.
They began dating after meeting on the set of 2007 movie Ten Inch Hero. The pair announced their happy baby news in January, saying they were "excited" to be starting a family together.
Jensen's baby means there will now be two youngsters on the Supernatural set; his co-star Jared Paladecki (Sam Winchester) became dad to son Thomas Colton in 2012.
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