There are several "characters" in the collected sonnets titled Astrophil and Stella by Sir Philip Sidney. Since it is a grouping of Sonnets, the brief vignettes change every so often, and the secondary characters are different throughout, but the concepts remain the same.

The most prominent characters featured in the sonnets are the titular characters, Astrophil and Stella.

Astrophil

Taken from the Greek words "Astro" meaning Star and "Phil" meaning Lover implies that Astrophil is the lover of the star. He is the narrator and main voice in the sonnets, speaking at length about his devotion and care for Stella, but all the while pining for her since they are distantly separated and can't be reconnected.

Stella

Taken from the Latin word meaning Star, Stella is the star which Astrophil loves and to whom he is devoted. She is separated from him, but he expresses an undying love for her, although he is frustrated because they will never be united. In reality, it appears Stella is modeled after Sidney's former lover, Lady Penelope Devereux, who was eventually married to Lord Rich. This marriage, while being unpleasant for her, is also the cause for their separation in the poem. The fact that her moniker is Latin and his Greek indicates this separation even further.

The Fates and other Forces

The Fates, Nature, and Reason are among some of the "characters" mentioned in the sonnets that prevent the two from being together. These unseen forces act as barriers and discourage them from attempting to reunite. There are a number of these forces mentioned throughout the story, and they all serve a similar purpose.

Rich/Riches

Not quite a character, but loosely alluded to, is Lord Rich. Stella is described as being "Rich" but her only poverty is that she is "Rich"—meaning the only deficiency Astrophil finds in Stella is that she belongs to Lord Rich. This is a very thinly veiled allusion to Lady Devereux's husband and the pain which their union causes for Sydney.