The slender seahorse or longsnout seahorse (Hippocampus reidi) is a species of fish in the family Syngnathidae.
The slender seahorse typically grows to be approximately 6.8 inches long (17.5 centimeters). Males and females are easily distinguished due to their bright colors. Males are usually orange, while the females are yellow. However, both males and females may have brown or white spots placed sporadically upon their body. These spots may also change into a pink or white color during the courtship period.
The slender seahorse has been found at depths of 55 meters. Smaller individuals inhabit shallower waters. The slender seahorse has an affinity for coral reefs and seagrass beds and can be found on gorgonian coral, seagrass, mangroves, and Sargassum. It is native to many countries, including the Bahamas, Barbados, Belize, Bermuda, Brazil, Colombia, Cuba, Grenada, Haiti, Jamaica, Panama, United States (Florida and North Carolina), and Venezuela. It inhabits subtropical regions, ranging from 29 degrees north to 25 degrees south and 133 degrees west to 40 degrees east.