B19

B19 or B-19 may refer to:


 * B19 (New York City bus), serving Brooklyn
 * Douglas XB-19, an experimental bomber aircraft
 * Parvovirus B19, the virus that causes fifth disease
 * Caro–Kann Defence ECO code in chess
 * Patient B-19
 * Boron-19 (B-19 or 19B), an isotope of boron
 * LNER Class B19, classified B2 until 1945