Formaldehyde ( for-MAL-di-hide, fər-) (systematic name methanal) is an organic compound with the chemical formula CH₂O and structure H−CHO, more precisely H₂C=O. The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions (formalin), which consists mainly of the hydrate CH₂(OH)₂. It is the simplest of the aldehydes (R−CHO). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year. It is mainly used in the production of industrial resins, e.g., for particle board and coatings. Small amounts also occur naturally.

फार्मल्डिहाइड (Formaldehyde) प्राकृतिक रूप से पाया जाने वाला एक कार्बनिक यौगिक है जिसका अणुसूत्र CH₂O है। यह सबसे सरल एल्डिहाइड है, इसमें एक -CHO ग्रूप पाया जाता है। इसको 'मेथेनैल' भी कहते हैं। इसका 'फार्मल्डिहाइड' नाम इसके फॉर्मिक अम्ल के समान होने और इससे सम्बन्धित होने के कारण पड़ा है।