1. The condition in which the male reproductive organs (stamens) of a flower mature before the female ones (carpels), thereby ensuring that self-fertilization does not occur. Examples of protandrous flowers are ivy and rosebay willowherb. Compare protogyny; homogamy. See also dichogamy.

2. The condition in some hermaphrodite or colonial invertebrates in which the male gonads or individuals are sexually mature before the female ones. Compare protogyny.