I kemi er en funktionel gruppe den del af et molekyle som bestemmer molekylets kemiske egenskaber og dermed hvilke reaktioner molekylet kan deltage i. Et molekyle kan indeholde mere end en funktionel gruppe, eller slet ingen.

Klasse Gruppe Formel Strukturformel Præfiks Suffiks Eksempel Acylhalid (syreklorid) Haloformyl RCOX 75px|Acyl halide haloformyl- -oylhalid Acetylklorid(Ethanoylklorid) Alkohol Hydroxyl ROH 60px|center|Hydroxyl hydroxy- -ol 90px|methanolMethanol Aldehyd Aldehyd RCHO 75px|Aldehyd oxo- -al 75px|acetaldehydeAcetaldehyd(Ethanal) Alkan Alkyl RH 75px|Alkyl alkyl- -an 75px|methanMethan Alken Alkenyl R2C=CR2 75px|Alken alkenyl- -en 75px|ethyleneEthylen(Ethen) Alkyn Alkynyl RC≡CR' 100px|Alkyn alkynyl- -yn 100px|acetyleneAcetylen(Ethyn) Amid Carboxamid RCONR2 75px|Amid carboxamido- -amid 75px|acetamidAcetamid(Ethanamid) Aminer Primær amin RNH2 75px|Primær amin amino- -amin 75px|methylaminMetylamin(Methanamin) Sekundær amin R2NH 75px|Sekundær amin amino- -amin 75px|dimethylaminDimethylamin Tertiær amin R3N 75px|Tertiær amin amino- -amin 75px|trimethylaminTrimethylamin Kvarternær ammoniumkation R4N+ 75px|Kvarternær ammoniumkation ammonio- -ammonium 150px|kolinKolin Azoforbindelse Azo(Diimid) RN2R' 75px|Azo.pngl azo- -diazen 150px|MethylorangeMethylorange(p-dimethylamino-azobenzensulfonsyre) Toluenderivater Benzyl RCH2C6H5RBn 75px|Benzyl benzyl- 1-(substituent)toluen 75px|BenzylbromidBenzylbromid(1-Bromtoluen) Carbonat Carbonatester ROCOOR 75px|Carbonat alkyl carbonat Carboxylat Carboxylat RCOO− 60px|center|Carboxylat 75px|Carboxylat carboxy- -oat 75px|NatriumacetatNatriumacetat(Natriumethanoat) Carboxylsyre Carboxyl RCOOH 75px|Carboxylsyre carboxy- -(carboxyl)syre 75px|EddikesyreEddikesyre(Ethansyre) Cyanater Cyanat ROCN 75px|Cyanat cyanato- alkyl cyanat Thiocyanat RSCN 75px|Thiocyanat thiocyanato- alkyl thiocyanat Æter Æter ROR' 60px|center|Æter alkoxy- alkyl-alkyl-æter 75px|DiætylæterDiætylæter(Ethoxyethan) Ester Ester RCOOR' Ester|75px alkyl-alkanoate 75px|ÆtylbutyratÆtylbutyrat(Ætylbutanoat) Haloalkan Halo RX 75px|Halidgruppe halo- alkylhalid 75px|ChlorethanChlorethan(Ætylklorid) Hydroperoxid Hydroperoxy ROOH 75px|Hydroperoxy hydroperoxy- alkylhydroperoxid 75px|MethylethylketonperoxidMethylethylketonperoxid Imin Primær ketimin RC(=NH)R' 75px|Imin imino- -imin Sekundær ketimin RC(=NR)R' | 75px|Imin | imino- || -imin

| Primær aldimin | RC(=NH)H | 75px|Imin | imino- || -imin

| Sekundær aldimin | RC(=NR')H | 75px|Imin | imino- || -imin

| Isocyanid || Isocyanid | RNC | | isocyano- | alkylisocyanid

| rowspan="2" | Isocyanater | Isocyanat || RNCO | 75px|Isocyanate | isocyanato- | alkylisocyanat | 75px|MethylisocyanatMethylisocyanat |- | Isothiocyanat || RNCS | 75px|Isothiocyanat | isothiocyanato- | alkylisothiocyanat | 100px|AllylisothiocyanatAllylisothiocyanat |- | Keton || Carbonyl | RCOR' | Keton|75px | keto-, oxo- || -on | 75px|ButanonMethylethylketon(Butanon)|- | Nitrat || Nitrat | RONO2 | 75px|Nitrat | nitrooxy-, nitroxy- || alkylnitrat | 150px|AmylnitratAmylnitrat(1-nitrooxypentan)|- | Nitril || Nitril | RCN | 75px|Nitril | cyano- || alkannitril alkylcyanid | 75px|BenzonitrilBenzonitril(Phenylcyanid)|- | Nitrit || Nitrosooxy | RONO | 75px|Nitrit | nitrosooxy- || alkylnitrit | 150px|AmylnitritAmylnitrit(3-methyl-1-nitrosooxybutan)|- | Nitroforbindelse | Nitro | RNO2 | 75px|Nitro | nitro- ||   | 75px|NitromethanNitromethan |- | Nitrosoforbindelse | Nitroso || RNO | 75px|Nitroso | nitroso- ||   | 75px|NitrosobenzenNitrosobenzen |- | Peroxid | Peroxy | ROOR | 75px|Peroxy | peroxy- | alkylperoxid | 75px|Di-tert-butylperoxidDi-tert-butylperoxid |- | Benzenderivater | Phenyl | RC6H5 | 75px|Phenyl | phenyl- || -benzen | 75px|CumeneCumene(2-phenylpropan)|-s | Fosfin || Fosfino | R3P | 75px|En tertiær phosphin | phosphino- || -phosphan | 75px|MethylpropylphosphanMethylpropylphosphan |- | Fosfodiester | Fosfat | HOPO(OR)2 | 75px|Fosfodiester | fosforsyre-di(substituent)ester | di(substituent)-hydrogenfosfat | DNA |- | Phosphosyre || Phosphono | RP(=O)(OH)2 | 75px|Phosphono group | phosphono- | substituent phosphonsyre | 75px|Benzylphosphonic acidBenzylphosphonic acid |- | Fosfat || Fosfat | ROP(=O)(OH)2 | 75px|Fosfatgruppe | phospho- || | 75px|Glyceraldehyde 3-phosphateGlyceraldehyd-3-fosfat |- | Pyridinderivater | Pyridyl | RC5H4N | 75px|4-pyridylgruppe 75px|3-pyridylgruppe 75px|2-pyridylgruppe | 4-pyridyl(pyridin-4-yl) 3-pyridyl(pyridin-3-yl) 2-pyridyl(pyridin-2-yl) | -pyridin | 75px|NicotinNicotin |- | Sulfid | | RSR' | 75px|Sulfidgruppe | | di(substituent)sulfid | 75px|DimethylsulfidDimethylsulfid |- | Sulfon | Sulfonyl | RSO2R' | 75px|Sulfonylgruppe | sulfonyl- | di(substituent)-sulfon | 75px|DimethylsulfonDimethylsulfon(Metylsulfonylmetan)|- | Sulfonsyre || Sulfo | RSO3H | 75px|Sulfonylgruppe | sulfo- | substituent-sulfonsyre | 75px|BenzenesulfonsyreBenzensulfonsyre |- | Sulfoxid | Sulfinyl | RSOR' | 75px|Sulfinylgruppe | sulfinyl- | di(substituent)-sulfoxid | 75px|DifenylsulfoxidDifenylsulfoxid |- | Thiol | Sulfhydryl | RSH | 75px|Sulfhydryl | mercapto-, sulfanyl- | -thiol | 75px|EthanthiolEthanthiol(Ethylmercaptan)''