There is no algorithm that, given a polynomial f∈Z[X1,…,Xn] with n part of the input, decides whether f has a zero in Qn. The proof reduces integer solvability to rational solvability through finite systems of rational constraints built from f, and shows that if all of them are solvable then f has an integer zero, using a formula that rules out odd poles and a height bound from odd contact with five points. Since integer solvability is undecidable, this answers the rational analogue of Hilbert's tenth problem negatively.