| Official Name: | Sant'Eustachio |
| Settlement Type: | Rione of Rome |
| Seal Size: | 100px |
| Mapsize: | 200px |
| Pushpin Label Position: | bottom |
| Subdivision Type: | Country |
| Subdivision Name: |  Italy |
| Subdivision Type1: | Region |
| Subdivision Name1: | Lazio |
| Subdivision Type2: | Province |
| Subdivision Name2: | Rome |
| Subdivision Type3: | Comune |
| Subdivision Name3: | Rome |
| Unit Pref: | Imperial |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
Sant'Eustachio (pronounced as /it/) is the 8th Italian: [[rioni of Rome|rione]] of Rome, Italy, identified by the initials R. VIII. It is named after the eponymous church and is located within the Municipio I.
Its coat of arms depicts the head of a stag with a cross between the antlers, symbol of Saint Eustace: the figure is golden on a red background.
Northward, Sant'Eustachio borders with Campo Marzio (R. IV), whose boundary is defined by Piazza in Campo Marzio, Via della Stelletta and Via dei Portoghesi. It also borders with Ponte, from which is separated by Via dei Pianellari, Piazza di Sant'Agostino, Via di Sant'Agostino and Piazza delle Cinque Lune.
To the west, the rione borders with Parione (R. VI), from which is separated by Piazza delle Cinque Lune, Corso del Rinascimento, Corso Vittorio Emanuele II, Largo dei Chiavari and Via dei Chiavari.
Southward, Sant'Eustachio borders with Regola (R. VII), the boundary being outlined by Via dei Giubbonari, Piazza Benedetto Cairoli, Via Arenula and Via di Santa Maria del Pianto; as well as with Sant'Angelo (R. XI), from which is separated by Via in Publicolis, Via dei Falegnami, Via di Sant'Elena and Largo Arenula.
Eastward, it borders with Pigna (R. IX), the boundary being defined by Largo Arenula, Via di Torre Argentina, Piazza di Santa Chiara and Via della Rotonda; and with Colonna (R. III), whose border is marked by Piazza della Rotonda, Via del Pantheon, Piazza della Maddalena and Via della Maddalena.