MCDD may refer to:

• Multiple complex developmental disorder
• McDonnell Douglas

• Euler–Liljestrand mechanism
• Euler–Maclaurin formula
• Euler–Maclaurin summation formula
• Euler–Mascheroni constant
• Euler–Rodrigues parameters
• Euler–Tricomi equation
• Euless, Texas
• Euless, TX
• EU liberalisation
• Eulipotyphla
• Eulithis mellinata
• Eulithis pyraliata
• Eulji Mundeok
• Eulji University
• EUL/NGL
• Eulogy
• Eulogy and Light
• Eulogy (film)
• Eulogy (movie)
• Eulonia
• Eulonia, Georgia
• Eulophia
• Eulophia decaryana
• Eulychnia
• Eulychnocactus