The Prime Minister is a novel by Anthony Trollope, published in 1876, and is the fifth installment in the "Palliser" series. The story revolves around Plantagenet Palliser, the Duke of Omnium, who becomes Prime Minister of a fragile coalition government formed when neither the Whigs nor the Tories can govern alone.Initially hesitant about his leadership abilities, Palliser gradually finds confidence in his role. However, he faces significant challenges due to the internal divisions within his government and his own rigid nature, which complicates his efforts to enact meaningful policies.

A central subplot involves Ferdinand Lopez, a socially ambitious man of ambiguous background who marries Emily Wharton against her father's wishes. Lopez's charm initially captivates Emily, but she soon discovers his many flaws. After a failed attempt to secure a parliamentary seat—encouraged by Lady Glencora Palliser, who hosts lavish gatherings to boost her husband's political standing—Lopez's fortunes decline. He becomes embroiled in a scandal involving election expenses that leads to public outrage and personal tragedy.