James Walker Fannin Jr. (January 1, 1804– March 27, 1836) was an American military officer, planter, and slave trader who served in the Texian Army during the Texas Revolution.

After being outnumbered and surrendering to the Mexican Army at the Battle of Coleto Creek, Fannin and his fellow prisoners of war were massacred soon afterward at Goliad, Texas, under Antonio López de Santa Anna's orders.

His mother was not married to his father, and he was adopted by his maternal grandfather, James W. Walker, and raised on a plantation in Marion, Georgia.

[2] He briefly attended the University of Georgia when he was 14, and later enrolled in the United States Military Academy at West Point on July 1, 1819.

[8] In Muscogee County, he was a member of the Temperance Society, master of the local Masonic lodge, and had attempted to become a judge, but was disqualified for his past of dueling.

[9][1] In 1834, Fannin settled his family at Velasco, in Tejas (now Texas), where he owned a slave plantation and was a managing partner in a slave-trading syndicate.

Fannin later worked with James Bowie, First Battalion, First Division, under Austin's orders to secure supplies and determine the conditions in and around Gonzales and San Antonio de Bexar: Fellow citizens ... We urge as many as can possibly leave their homes to repair to Gonzales immediately, "armed and equipped for war even to the knife."

...If Texas will now act promptly, she will soon be redeemed from that worse than Egyptian bondage which now cramps her resources and retards her prosperity.Under the command of Bowie,[13] Fannin fought in the Battle of Concepción on October 28, 1835.

[15] Sam Houston, supported by Governor Henry Smith, commissioned Fannin as a colonel in the regular army on December 7, 1835.

[16] In early February, Fannin sailed from Velasco and landed at Copano with four companies of the Georgia Battalion, moving to join a small band of Texians at Refugio.

Mexican reinforcements under General Jose Urrea arrived at Matamoros, complicating the Texian plans to attack that city.

Appeals from Travis at the Alamo (via James Bonham) prompted Fannin to launch a relief march of more than 300 men and four pieces of artillery on February 25, 1836.

The troops barely had crossed the San Antonio River when wagons broke down, prompting the men to camp within sight of Goliad.

[20] King and his men confronted an advance party of General Urrea's cavalry in the Battle of Refugio; his defense failed and he withdrew to the old mission.

[22] Fannin needed means of transport and had sent Albert C. Horton and his men to Victoria, to bring carts and 20 yokes of oxen from Army quartermaster John J. Linn, who did return around March 16.

The Texians immediately formed a hollow square with their wagons and cannon placed in each corner for defense as Urrea's forces attacked.

Under a decree that Santa Anna had pressed for, and which was passed by the Mexican Congress on December 30, 1835, armed foreigners taken in combat were to be treated as pirates and executed.