Margaret Lea Houston (April 11, 1819 – December 3, 1867) was First Lady of the Republic of Texas during her husband Sam Houston's second term as President of the Republic of Texas. They met following the first of his two non-consecutive terms as the Republic's president, and married when he was a representative in the Congress of the Republic of Texas. She was his third wife, remaining with him until his death.

She came from a close-knit family in Alabama, many of whom also moved to Texas when she married the man who was an accomplished politician in both Tennessee and Texas, and who had won the Battle of San Jacinto during the Texas Revolution. The couple had eight children, and she gave birth to most of them while he was away attending to politics. Her mother Nancy Lea was a constant in their lives, helping with the children, managing the household help, and always providing either financial assistance or temporary housing. With the help of her extended family in Texas, Margaret convinced her husband to give up both alcohol and profane language. He believed his wife to be an exemplary woman of faith and, under her influence, converted to the Baptist denomination, after he had many years earlier been baptized a Catholic in Nacogdoches, Texas.

Following the Annexation of Texas to the United States, Sam Houston shuttled back and forth to Washington, D.C. as the state's U.S. senator for 13 years, while Margaret remained in Texas raising their children. When he was elected the state's governor, Margaret became First Lady of the state of Texas and was pregnant with their last child. Her brief tenure came on the cusp of the Civil War, at a time when the state was torn apart over the debate of whether or not to secede from the United States, while her husband worked in vain to defeat the Texas Ordinance of Secession. There was an attempt on his life, and angry mobs gathered in the streets near the governor's mansion. With no government protection provided, she lived in fear for her family's safety.

Her husband was removed from office by the Texas Secession Convention for refusing to swear loyalty to the Confederacy. Margaret became a wartime mother, whose eldest son joined the Confederate Army and was taken prisoner at the Battle of Shiloh. Her husband died before the end of the war. In her few remaining years, she became the keeper of the Sam Houston legacy and opened his records to a trusted biographer. When she died of yellow fever four and a half years later, Margaret could not be buried with her husband in a public cemetery in Huntsville for fear of contamination, and was instead interred next to her mother on private property.

Margaret Moffette Lea was born April 11, 1819, into a family of devout Baptists in Perry County, Alabama. Her father Temple Lea was a church deacon and the state treasurer of the Alabama Baptist Convention, and her mother Nancy Moffette Lea was the only woman delegate at the convention's formation. Margaret was the fifth of six children that included older brothers Martin, Henry Clinton and Vernal, older sister Varilla, and younger sister Antoinette. The Lea cotton plantation had been acquired with money from a Moffette family inheritance, and was operated by Nancy.

When her father died in 1834, she inherited five slaves: Joshua, Eliza, her favorite, Viannah, Charlotte and Jackson. The older Lea children had married prior to Temple's death, but Vernal, Margaret and Antoinette accompanied the widowed Nancy when she moved into her son Henry's home at Marion. He was an accomplished attorney who sat on the boards of educational institutions, and would be elected to the Alabama State Senate in 1836. Margaret was enrolled at Professor McLean's School, and also attended Judson Female Institute. The latter was founded by Baptists to instruct genteel young women in what were considered acceptable goals of their time and place, "proficiency in needlework, dancing, drawing, and penmanship". Heavy emphasis was put on Baptist theology and missionary work. She wrote poetry and read romantic novels, while also becoming accomplished on guitar, harp and piano. Reverend Peter Crawford baptized her in the Siloam Baptist Church of Marion when she was 19, by which time the eligible young lady was considered "accomplished, well-connected and deeply religious".

Sam Houston was an attorney by profession and politically accomplished even before he moved to Texas. In Tennessee, he had been both a member of the United States House of Representatives and governor. His military victory at the Battle of San Jacinto elevated him to hero status in Texas. After completing his first term as President of the Republic of Texas in early December 1838, he continued to practice law from his office in Liberty. He arrived in Mobile, Alabama, in the early months of 1839 as a partner of the Sabine City Company, seeking investors to develop a community that is today known as Sabine Pass. Through Martin Lea, he made the acquaintance of Antoinette's husband William Bledsoe, a wealthy businessman who in turn suggested Nancy Lea as a possible investor. Invited to a garden party at Martin's home, it was there Houston first became acquainted with Margaret. The mutual attraction was instantaneous.

Nancy was favorably impressed with Houston's land sales pitch, but not so impressed with his interest in her daughter. She and others in the family were concerned about his reputation as a hard-drinking carouser with a proclivity for profanity, who was 26 years older than Margaret and twice married. Several weeks of love letters had been exchanged between Margaret and Houston by the time he proposed marriage that summer of 1839, presenting her with his image carved on a brooch. In an effort to assuage the family's opposition to the union, Houston spent several weeks in the Lea home in Alabama.