A donor portrait or votive portrait is a portrait in a larger painting or other work showing the person who commissioned and paid for the image, or a member of his, or (much more rarely) her, family. Donor portrait usually refers to the portrait or portraits of donors alone, as a section of a larger work, whereas votive portrait may often refer to a whole work of art intended as an ex-voto, including for example a Madonna, especially if the donor is very prominent. The terms are not used very consistently by art historians, as Angela Marisol Roberts points out, and may also be used for smaller religious subjects that were probably made to be retained by the commissioner rather than donated to a church.

Donor portraits are very common in religious works of art, especially paintings, of the Middle Ages and Renaissance, the donor usually shown kneeling to one side, in the foreground of the image. Often, even late into the Renaissance, the donor portraits, especially when of a whole family, will be at a much smaller scale than the principal figures, in defiance of linear perspective. By the mid-15th century donors began to be shown integrated into the main scene, as bystanders and even participants.

The purpose of donor portraits was to memorialize the donor and his family, and especially to solicit prayers for them after their death. Gifts to the church of buildings, altarpieces, or large areas of stained glass were often accompanied by a bequest or condition that masses for the donor be said in perpetuity, and portraits of the persons concerned were thought to encourage prayers on their behalf during these, and at other times. Displaying portraits in a public place was also an expression of social status; donor portraits overlapped with tomb monuments in churches, the other main way of achieving these ends, although donor portraits had the advantage that the donor could see them displayed in his own lifetime.

Furthermore, donor portraits in Early Netherlandish painting suggest that their additional purpose was to serve as role models for the praying beholder during his own emotional meditation and prayer – not in order to be imitated as ideal persons like the painted Saints but to serve as a mirror for the recipient to reflect on himself and his sinful status, ideally leading him to a knowledge of himself and God. To do so during prayer is in accord with late medieval concepts of prayer, fully developed by the Modern Devotion. This process may be intensified if the praying beholder is the donor himself.

When a whole building was financed, a sculpture of the patron might be included on the facade or elsewhere in the building. Jan van Eyck's Rolin Madonna is a small painting where the donor Nicolas Rolin shares the painting space equally with the Madonna and Child, but Rolin had given great sums to his parish church, where it was hung, which is represented by the church above his praying hands in the townscape behind him.

Sometimes, as in the Ghent Altarpiece, the donors were shown on the closed view of an altarpiece with movable wings, or on both the side panels, as in the Portinari Altarpiece and the Memlings above, or just on one side, as in the Mérode Altarpiece. If they are on different sides, the males are normally on the left for the viewer, the honorific right-hand placement within the picture space. In family groups the figures are usually divided by gender. Groups of members of confraternities, sometimes with their wives, are also found. Additional family members, from births or marriages, might be added later, and deaths might be recorded by the addition of small crosses held in the clasped hands.

At least in Northern Italy, as well as the grand altarpieces and frescos by leading masters that attract most art-historical attention, there was a more numerous group of small frescoes with a single saint and donor on side-walls, that were liable to be re-painted as soon as the number of candles lit before them fell off, or a wealthy donor needed the space for a large fresco-cycle, as portrayed in a 15th-century tale from Italy:

And going around with the master mason, examining which figures to leave and which to destroy, the priest spotted a Saint Anthony and said: 'Save this one.' Then he found a figure of Saint Sano and said: 'This one is to be gotten rid of, since as long as I have been the Priest here I have never seen anyone light a candle in front of it, nor has it ever seemed to me useful; therefore, mason, get rid of it.'