The person widely regarded as the first computer programmer is Ada Lovelace.

Augusta Ada King, Countess of Lovelace (1815-1852), was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed mechanical general-purpose computer, the Analytical Engine. In her notes on the engine, she described an algorithm for the machine to compute Bernoulli numbers. This algorithm is considered the first algorithm intended to be processed by a machine; therefore, she is often credited as the first computer programmer.

For more information, you can refer to these sources:

• Computer History Museum - Ada Lovelace
• Britannica - Ada Lovelace