The 34-year-old, whose husband is investment banker Marc Mezvinsky, tweeted the news to her 624,000 followers shortly after midnight tonight - four days before the expected due date.
She said: 'Marc and I are full of love, awe and gratitude as we celebrate the birth of our daughter, Charlotte Clinton Mezvinsky.'
The baby is the first grandchild of Bill and Hillary Clinton, who have gushed at length about their excitement at a number of public speaking events in the past few months, and both retweeted their daughter's post tonight.
Chelsea was last seen on Wednesday afternoon at the annual Clinton Global Initiative summit in New York's Sheraton Hotel, where she had been on her feet for three days straight.
Despite resigning from her position as a specialist reporter for NBC in April, the former First Daughter, who was educated at Stanford, Oxford and Columbia universities, continued to work full-time for the Clinton Foundation up until she gave birth.
News of the birth - four days before the expected due date - will come as welcome news to supporters of Hillary Clinton running for president since the former First Lady said she would wait until she became a grandmother before launching a second bid for the nomination.
A spokesman for the new parents, Kamyl Bazbaz, confirmed Clinton had the child on Friday.
On Tuesday, Chelsea appeared on CNN with her growing baby bump as she revealed they had decided not to find out the gender of their first child until the birth as they wanted it to be a surprise.
'There are so few mysteries in life...any answer is a happy one,' Clinton told CNN's Fareed Zakaria on Tuesday.
'So my husband and I decided that we would enjoy this mystery for the nine-plus months that we're granted, and we are eager to find out what God will have given us.'
The name Charlotte dates back to the 1700s, and means 'freedom'.
It has long been a favourite among royals and political dynasties, and last year it was the 11th most popular girl names in the United States.
美国前总统比尔•克林顿与妻子、前国务卿希拉里的第一个外孙出生了!综合外国媒体报道,美国东部时间9月26日晚,克林顿夫妇的独生女切尔西产下一个女儿,取名为“夏洛特”。
“我们的女儿,夏洛特•克林顿•梅兹文斯基,出生了!马克和我对此满怀爱意、敬畏和感激。”26日晚10时,切尔西在其“脸谱网”(Facebook)和“推特网”(Twitter)账号上发表上述声明,宣布克林顿家族多了一位新成员。
随后,新晋为外祖父祖母的克林顿和希拉里在各自的“推特网”账号上转发了这一喜讯。
现年34岁的切尔西在今春宣布怀孕。上月底,她辞去美国全国广播公司(NBC)的记者职务,专注于克林顿基金会的公务同时安心待产。对于腹中胎儿的性别和预产期,切尔西夫妇一直对外界保密甚严。本月21日,克林顿在一个采访中说漏嘴称他将在10月1日前当上外祖父。
作为全美最受关注的政治家之一,希拉里把外孙的出生同她的仕途联系起来,她说希望先当上外祖母,而后再决定是否参加2016年总统选举。不过,她同时暗示新生命的降临也可能给她再次竞选总统的理由。
英国路透社称,目前尚不清楚第一个外孙的来临会对希拉里的政治野心产生何种影响,但克林顿曾公开表示:“我希望我的妻子过得开心,而她只有当上外祖母才能真正感到喜悦……这是她想要的东西,更胜于当总统。”
“夏洛特”这个名字起源于18世纪,寓意是“自由”。
在王室和政治世家,“夏洛特”一直是最钟爱的名字之一,去年在美国最受欢迎女孩名字排行榜上名列第十一。
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