Count: 0 — No single-word English prepositions or widely accepted multi-word prepositional phrases begin with the letter X. This list targets single-word prepositions and prepositional phrases whose first word starts with X. Interesting detail: X is one of the rarest initial letters in English, and most X‑initial words are later borrowings that serve as nouns or adjectives rather than function words.

Consult Oxford, Cambridge, and Merriam‑Webster and check large corpora such as COCA and the BNC: none record a standard X‑initial preposition. Understand that prepositions form a small, closed class of words with deep Old English and Germanic roots, while X‑initial vocabulary typically comes from Greek or other borrowings and fills open-class roles (nouns, verbs, adjectives).

Consider close cases and practical alternatives: no common multi‑word prepositional phrase begins with X either. Note that Latin ex (meaning “out of”) appears in set Latin phrases, but English transcriptions and standard prepositions do not use an X‑initial standalone preposition. When you need X‑related material, look for content words and prefixes (xeno‑, xylo‑) or consult the broader A–Z preposition list for functional words starting with other letters.