Mathilde Loisel is the main character in the short story "The Necklace" by Guy de Maupassant. She is portrayed as a beautiful but dissatisfied woman who dreams of a more luxurious life. Mathilde feels that she deserves wealth and elegance, which leads her to envy others who possess these qualities. Her desire for a glamorous lifestyle drives her to borrow a diamond necklace for a high-society event. After losing the necklace, Mathilde and her husband endure years of hardship to repay the debt, ultimately leading to a harsh realization about the value of appearances and the consequences of her aspirations.