Princess Ningguo of the Ming Dynasty (宁国公主,1364 –‍ 7 September 1434), personal name Zhu Changning, was a royal princess of Ming Dynasty. She was the First daughter of Hongwu Emperor Zhu Yuanzhang the founding emperor of the Ming dynasty through his wife, Empress Xiaocigao, but his Second daughter in general and Second daughter to survive into adulthood.
She was the wife of Mei Yin, the nephew of Runan Hou Meisizu and had two sons (maybe three).
Early life.
In 1364, Zhu Changning was born probably in Yingtian Fu (later Nanjing) to the then Zhu Yuanzhang (Later Hongwu Emperor) and Empress Xiaocigao.
In 1368, When Zhu Changning was 4 years old her father Zhu Yuanzhang founded the Ming dynasty and became the Hongwu Emperor and appointed her mother as Empress Xiaocigao and Zhu Yuanzhang held great respect and affection for Empress Xiaocigao, which resulted in Princess Ningguo being cherished from a young age.
Married life.
In 1378, When Zhu Changning was fourteen years old, she was granted the title of Princess Ningguo and married Mei Yin, the nephew of Mei Sizu, the Marquis of Runan and this marriage produced two sons. Among the sixteen consorts in the court, Mei Yin was especially favored by Zhu Yuanzhang. At that time, Li Wenzhong held the post of Duke of Shang and was responsible for overseeing national studies, while Mei Yin served as the governor of Shandong Province. Recognizing his remarkable command of the classics and history, Zhu Yuanzhang issued an edict praising him—a commendation that earned Mei Yin the respect of all the court’s officials .
In the later years of Zhu Yuanzhang’s reign, as the power of the various vassal kings increased, he discreetly assigned Mei Yin to support Emperor Jianwen. In December of the third year of Jianwen’s rule (1401), Mei Yin was ordered to guard Huai'an, a post he took very seriously by enforcing strict defensive measures. 
Later, he led troops to resist the attack launched by Zhu Di, the Prince of Yan. At that time, Zhu Di compelled Princess Ningguo to compose a blood letter intended to force Mei Yin’s surrender. Upon receiving the letter, Mei Yin was overcome with grief—Upon receiving word of Emperor Jianwen's death, Mei Yin was overcome with despair and had to return to Nanjing. There, he discovered that Zhu Di had ascended the throne. In an apparent attempt to conceal the true circumstances of his rise to power, Zhu Di personally left the city to greet Mei Yin. However, Mei Yin's chilly reception deeply offended him. Over time, Mei Yin's continued disregard for Zhu Di led to increasing tensions. 
In 1405,Emperor Zhu Di orchestrated a plot and had the Jinyiwei drown Mei Yin, falsely claiming that he had committed suicide.
Later life and death.
Someone eventually revealed the truth behind Mei Yin's death to Princess Ningguo. Overcome with grief, she rushed into the palace, grabbed Zhu Di's sleeve, and wept bitterly. To console her, Zhu Di conferred official positions upon her two sons. Shortly after her return home, Zhu Di sent her a letter clarifying that he had not been responsible for Mei Yin's death—that the true murderer had been found and brought to justice—in hopes of easing her sorrow.
Soon after this, the princess was promoted to the title of Ningguo Dachanggong (Grand Princess) .In the following years, Zhu Di further rewarded her with abundant gold and silver treasures. In the 22nd year of the Yongle reign, her title was reaffirmed. Ultimately, Princess Ningguo spent the remainder of her life, until her passing at the age of 71, devoted to safeguarding her two sons.