Aries belongs to the element of Fire and moves through life in the Cardinal mode, ruled by Mars. Sagittarius belongs to the element of Fire and moves in the Mutable mode, ruled by Jupiter.
Two fire signs share a pulse of enthusiasm, courage and drive. The spark is instant and the pace is brisk — the risk is that there is no one left to slow the fire down when it burns hot.
The cardinal partner points the direction; the mutable partner finds the graceful route there. A naturally collaborative dynamic, as long as the direction is clear and not quietly assumed.
Both signs belong to the active, outward polarity, so your life together tends to be social, expressive and forward-moving. Give each other permission to pause sometimes.
What follows is a general read on this pair. Real compatibility depends on the whole natal chart — use the calculator linked on this page to compare two full charts when you're ready.