A sentimental ballad is an emotional style of music that often deals with romantic and intimate relationships, and to a lesser extent, loneliness, death, war, drug abuse, politics and religion, usually in a poignant but solemn manner. Ballads are generally melodic enough to capture the listener's attention.

Sentimental ballads are found in most music genres, such as pop, R&B, soul, country, folk, rock and electronic music. Usually slow in tempo, ballads tend to have a lush musical arrangement which emphasizes the song's melody and harmonies. Characteristically, ballads use acoustic instruments such as guitars, pianos, saxophones, and sometimes an orchestral set. Many modern mainstream ballads tend to feature synthesizers, drum machines and even, to some extent, a dance rhythm.

Sentimental ballads had their origins in the early Tin Pan Alley music industry of the later 19th century. Initially known as "tear-jerkers" or "drawing-room ballads", they were generally sentimental, narrative, strophic songs published separately or as part of an opera, descendants perhaps of broadside ballads. As new genres of music began to emerge in the early 20th century, their popularity faded, but the association with sentimentality led to the term ballad being used for a slow love song from the 1950s onwards.

Sentimental ballads have their roots from medieval French chanson balladée or ballade, which were originally "danced songs". Ballads were particularly characteristic of the popular poetry and song of the British Isles from the later medieval period until the 19th century. They were widely used across Europe, and later in the Americas, Australia and North Africa. As a narrative song, their theme and function may originate from Scandinavian and Germanic traditions of storytelling. Musically they were influenced by the Minnesinger. The earliest example of a recognizable ballad in form in England is "Judas" in a 13th-century manuscript. A reference in William Langland's Piers Plowman indicates that ballads about Robin Hood were being sung from at least the late 14th century and the oldest detailed material is Wynkyn de Worde's collection of Robin Hood ballads printed about 1495.

Ballads at this time were originally composed in couplets with refrains in alternate lines. These refrains would have been sung by the dancers in time with the dance. In the 18th century, ballad operas developed as a form of English stage entertainment, partly in opposition to the Italian domination of the London operatic scene. In America a distinction is drawn between ballads that are versions of European, particularly British and Irish songs, and 'Native American ballads', developed without reference to earlier songs. A further development was the evolution of the blues ballad, which mixed the genre with Afro-American music.

In the late 19th century, Danish folklorist Svend Grundtvig and Harvard professor Francis James Child attempted to record and classify all the known ballads and variants in their chosen regions. Since Child died before writing a commentary on his work it is uncertain exactly how and why he differentiated the 305 ballads printed that would be published as The English and Scottish Popular Ballads. There have been many different and contradictory attempts to classify traditional ballads by theme, but commonly identified types are the religious, supernatural, tragic, love ballads, historic, legendary and humorous.

By the Victorian era, ballad had come to mean any sentimental popular song, especially so-called "royalty ballads", for which publishers would pay a star singer to promote new songs in exchange for a lump sum or a "royalty signature" on the sheet music and a small percentage of sales. Some of Stephen Foster's songs exemplify this genre and, in England, the ballads of Montague Phillips written for his wife Clara Butterworth in the early 1900s. By the 1920s, composers of Tin Pan Alley and Broadway used ballad to signify a slow, sentimental tune or love song, often written in a fairly standardized form. Jazz musicians sometimes broaden the term still further to embrace all slow-tempo pieces. Notable sentimental ballads of this period include, "Little Rosewood Casket" (1870), "After the Ball" (1892), and "Danny Boy" (1913).

Popular sentimental ballad vocalists in this era include Frank Sinatra, Ella Fitzgerald, Andy Williams, Johnny Mathis, Connie Francis and Perry Como. Their recordings were usually lush orchestral arrangements of current or recent rock and roll or pop hit songs. The most popular and enduring songs from this style of music are known as "pop standards" or (where relevant) "American standards". Many vocalists became involved in 1960s' vocal jazz and the rebirth of swing music, which was sometimes referred to as "easy listening" and was, in essence, a revival of popularity of the "sweet bands" that had been popular during the swing era, but with more emphasis on the vocalist and the sentimentality.