Exhibit 8.1



Subsidiaries of Ecopetrol S.A.



The following table sets forth our subsidiaries,
their respective countries of incorporation, our percentage ownership in each (both directly and indirectly through other subsidiaries)
at March 31, 2018.



|COMPANY                                                |  | COUNTRY OF INCORPORATION |  | OWNERSHIP |       
|------------------------------------------------------ |  | ------------------------ |  | --------- | ------
|ANDEAN CHEMICALS LIMITED                               |  | Bermuda                  |  |           | 100.00
|BLACK GOLD RE LIMITED                                  |  | Bermuda                  |  |           | 100.00
|CENIT TRANSPORTE Y LOGÍSTICA DE HIDROCARBUROS S.A.S.   |  | Colombia                 |  |           | 100.00
|ECOPETROL CAPITAL AG                                   |  | Switzerland              |  |           | 100.00
|ECOPETROL GLOBAL ENERGY S.L.U.                         |  | Spain                    |  |           | 100.00
|ECOPETROL GLOBAL CAPITAL S.L.U. ***                    |  | Spain                    |  |           | 100.00
|EQUION ENERGÍA LIMITED                                 |  | United Kingdom           |  |           | 51.00 
|HOCOL PETROLEUM LIMITED                                |  | Bermuda                  |  |           | 100.00
|BIOENERGY S.A.S.**                                     |  | Colombia                 |  |           | 99.10 
|BIOENERGY ZONA FRANCA S.A.S.**                         |  | Colombia                 |  |           | 99.10 
|COLOMBIA PIPELINES LIMITED**                           |  | United Kingdom           |  |           | 51.00 
|COMPOUNDING AND MASTERBATCHING INDUSTRY LTDA - COMAI** |  | Colombia                 |  |           | 100.00
|ECOPETROL AMERICA INC**                                |  | United States            |  |           | 100.00
|ECOPETROL DEL PERU S.A.**                              |  | Peru                     |  |           | 100.00
|ECOPETROL OLEO & GAS DO BRASIL LTDA**                  |  | Brazil                   |  |           | 100.00
|ECP OIL AND GAS GERMANY GMBH**                         |  | Germany                  |  |           | 100.00
|HOCOL S.A.**                                           |  | Cayman Islands           |  |           | 100.00
|OLEODUCTO BICENTENARIO DE COLOMBIA S.A.S.**            |  | Colombia                 |  |           | 55.97 
|OLEODUCTO CENTRAL S.A. - OCENSA**                      |  | Colombia                 |  |           | 72.65 
|OLEODUCTO DE COLOMBIA S.A. - ODC**                     |  | Colombia                 |  |           | 73.00 
|OLEODUCTO DE LOS LLANOS  ORIENTALES  S.A.**            |  | Panama                   |  |           | 65.00 
|REFINERIA DE CARTAGENA S.A. *                          |  | Colombia                 |  |           | 100.00
|PROPILCO S.A.*                                         |  | Colombia                 |  |           | 100.00
|SANTIAGO OIL COMPANY**                                 |  | Cayman Islands           |  |           | 51.00 
|ESENTTIA RESINAS DEL PERU SAC**                        |  | Peru                     |  |           | 100.00
|ECP Hidrocarburos de México **                         |  | Mexico                   |  |           | 100.00
|ECOPETROL ENERGÍA SAS ESP **                           |  | Colombia                 |  |           | 100.00
|ECOPETROL COSTA AFUERA COLOMBIA S.A.S.**               |  | Colombia                 |  |           | 100.00



*Direct and indirect participation.
**Solely indirect participation through other subsidiaries or affiliates.

*** Ecopetrol Global Capital S.L.U. was liquidated on April
4, 2018.