diff --git a/Cargo.toml b/Cargo.toml
index b8f806474..3ecd2a8c9 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -71,6 +71,7 @@ indexmap = "2.3.0"
 fxhash = "0.2.1"
 bumpalo = { version = "3.16.0" }
 pathsearch = "0.2.0"
+base64 = "0.22.1"
 
 [profile.dev.package]
 insta.opt-level = 3
diff --git a/hugr-core/src/import.rs b/hugr-core/src/import.rs
index 6a08b4a78..828047ea2 100644
--- a/hugr-core/src/import.rs
+++ b/hugr-core/src/import.rs
@@ -922,7 +922,7 @@ impl<'a> Context<'a> {
             model::Term::Var { .. } => Err(error_unsupported!("type variable as `TypeParam`")),
             model::Term::Apply { .. } => Err(error_unsupported!("custom type as `TypeParam`")),
             model::Term::ApplyFull { .. } => Err(error_unsupported!("custom type as `TypeParam`")),
-
+            model::Term::BytesType { .. } => Err(error_unsupported!("`bytes` as `TypeParam`")),
             model::Term::Const { .. } => Err(error_unsupported!("`(const ...)` as `TypeParam`")),
             model::Term::FuncType { .. } => Err(error_unsupported!("`(fn ...)` as `TypeParam`")),
 
@@ -946,6 +946,7 @@ impl<'a> Context<'a> {
             | model::Term::Control { .. }
             | model::Term::NonLinearConstraint { .. }
             | model::Term::ConstFunc { .. }
+            | model::Term::Bytes { .. }
             | model::Term::ConstAdt { .. } => Err(model::ModelError::TypeError(term_id).into()),
 
             model::Term::ControlType => {
@@ -999,6 +1000,8 @@ impl<'a> Context<'a> {
             model::Term::Constraint => Err(error_unsupported!("`constraint` as `TypeArg`")),
             model::Term::StaticType => Err(error_unsupported!("`static` as `TypeArg`")),
             model::Term::ControlType => Err(error_unsupported!("`ctrl` as `TypeArg`")),
+            model::Term::BytesType => Err(error_unsupported!("`bytes` as `TypeArg`")),
+            model::Term::Bytes { .. } => Err(error_unsupported!("`(bytes ..)` as `TypeArg`")),
             model::Term::Const { .. } => Err(error_unsupported!("`const` as `TypeArg`")),
             model::Term::ConstAdt { .. } => Err(error_unsupported!("adt constant as `TypeArg`")),
             model::Term::ConstFunc { .. } => {
@@ -1126,6 +1129,8 @@ impl<'a> Context<'a> {
             | model::Term::ControlType
             | model::Term::Nat(_)
             | model::Term::NonLinearConstraint { .. }
+            | model::Term::Bytes { .. }
+            | model::Term::BytesType
             | model::Term::ConstFunc { .. }
             | model::Term::ConstAdt { .. } => Err(model::ModelError::TypeError(term_id).into()),
         }
@@ -1363,6 +1368,8 @@ impl<'a> Context<'a> {
             | model::Term::Control { .. }
             | model::Term::ControlType
             | model::Term::Type
+            | model::Term::Bytes { .. }
+            | model::Term::BytesType
             | model::Term::NonLinearConstraint { .. } => {
                 Err(model::ModelError::TypeError(term_id).into())
             }
diff --git a/hugr-model/Cargo.toml b/hugr-model/Cargo.toml
index e23ef3a6e..d1e3636b9 100644
--- a/hugr-model/Cargo.toml
+++ b/hugr-model/Cargo.toml
@@ -16,6 +16,7 @@ license.workspace = true
 bench = false
 
 [dependencies]
+base64 = { workspace = true }
 bumpalo = { workspace = true, features = ["collections"] }
 capnp = "0.20.1"
 derive_more = { version = "1.0.0", features = ["display"] }
diff --git a/hugr-model/capnp/hugr-v0.capnp b/hugr-model/capnp/hugr-v0.capnp
index 060e8af3b..a06665d1d 100644
--- a/hugr-model/capnp/hugr-v0.capnp
+++ b/hugr-model/capnp/hugr-v0.capnp
@@ -157,6 +157,8 @@ struct Term {
         nonLinearConstraint @20 :TermId;
         constFunc @22 :RegionId;
         constAdt @23 :ConstAdt;
+        bytes @24 :Data;
+        bytesType @25 :Void;
     }
 
     struct Apply {
diff --git a/hugr-model/src/v0/binary/read.rs b/hugr-model/src/v0/binary/read.rs
index 2ea0e7742..69ef45b14 100644
--- a/hugr-model/src/v0/binary/read.rs
+++ b/hugr-model/src/v0/binary/read.rs
@@ -335,6 +335,11 @@ fn read_term<'a>(bump: &'a Bump, reader: hugr_capnp::term::Reader) -> ReadResult
             let values = model::TermId(reader.get_values());
             model::Term::ConstAdt { tag, values }
         }
+
+        Which::Bytes(bytes) => model::Term::Bytes {
+            data: bump.alloc_slice_copy(bytes?),
+        },
+        Which::BytesType(()) => model::Term::BytesType,
     })
 }
 
diff --git a/hugr-model/src/v0/binary/write.rs b/hugr-model/src/v0/binary/write.rs
index 3a1e1beba..56511ba12 100644
--- a/hugr-model/src/v0/binary/write.rs
+++ b/hugr-model/src/v0/binary/write.rs
@@ -217,6 +217,14 @@ fn write_term(mut builder: hugr_capnp::term::Builder, term: &model::Term) {
             builder.set_tag(*tag);
             builder.set_values(values.0);
         }
+
+        model::Term::Bytes { data } => {
+            builder.set_bytes(data);
+        }
+
+        model::Term::BytesType => {
+            builder.set_bytes_type(());
+        }
     }
 }
 
diff --git a/hugr-model/src/v0/mod.rs b/hugr-model/src/v0/mod.rs
index f9da742e9..a5c98c8fb 100644
--- a/hugr-model/src/v0/mod.rs
+++ b/hugr-model/src/v0/mod.rs
@@ -686,6 +686,15 @@ pub enum Term<'a> {
         /// The values of the variant.
         values: TermId,
     },
+
+    /// A literal byte string.
+    Bytes {
+        /// The data of the byte string.
+        data: &'a [u8],
+    },
+
+    /// The type of byte strings.
+    BytesType,
 }
 
 /// A part of a list term.
diff --git a/hugr-model/src/v0/text/hugr.pest b/hugr-model/src/v0/text/hugr.pest
index 3d37b9878..1e12b1839 100644
--- a/hugr-model/src/v0/text/hugr.pest
+++ b/hugr-model/src/v0/text/hugr.pest
@@ -10,6 +10,8 @@ string_raw     = @{ (!("\\" | "\"") ~ ANY)+ }
 string_escape  = @{ "\\" ~ ("\"" | "\\" | "n" | "r" | "t") }
 string_unicode = @{ "\\u" ~ "{" ~ ASCII_HEX_DIGIT+ ~ "}" }
 
+base64_string = { "\"" ~ (ASCII_ALPHANUMERIC | "+" | "/")* ~ "="* ~ "\"" }
+
 module = { "(" ~ "hugr" ~ "0" ~ ")" ~ meta* ~ node* ~ EOI }
 
 meta = { "(" ~ "meta" ~ symbol ~ term ~ ")" }
@@ -97,6 +99,8 @@ term = {
   | term_non_linear
   | term_const_func
   | term_const_adt
+  | term_bytes_type
+  | term_bytes
 }
 
 term_wildcard     = { "_" }
@@ -122,5 +126,7 @@ term_ctrl_type    = { "ctrl" }
 term_non_linear   = { "(" ~ "nonlinear" ~ term ~ ")" }
 term_const_func   = { "(" ~ "fn" ~ term ~ ")" }
 term_const_adt    = { "(" ~ "tag" ~ tag ~ term* ~ ")" }
+term_bytes_type   = { "bytes" }
+term_bytes        = { "(" ~ "bytes" ~ base64_string ~ ")" }
 
 spliced_term = { term ~ "..." }
diff --git a/hugr-model/src/v0/text/parse.rs b/hugr-model/src/v0/text/parse.rs
index 34435b2a3..09d6413c9 100644
--- a/hugr-model/src/v0/text/parse.rs
+++ b/hugr-model/src/v0/text/parse.rs
@@ -1,3 +1,4 @@
+use base64::{prelude::BASE64_STANDARD, Engine};
 use bumpalo::{collections::String as BumpString, collections::Vec as BumpVec, Bump};
 use fxhash::FxHashMap;
 use pest::{
@@ -262,6 +263,20 @@ impl<'a> ParseContext<'a> {
                     Term::ConstAdt { tag, values }
                 }
 
+                Rule::term_bytes_type => Term::BytesType,
+
+                Rule::term_bytes => {
+                    let token = inner.next().unwrap();
+                    let slice = token.as_str();
+                    // Remove the quotes
+                    let slice = &slice[1..slice.len() - 1];
+                    let data = BASE64_STANDARD.decode(slice).map_err(|_| {
+                        ParseError::custom("invalid base64 encoding", token.as_span())
+                    })?;
+                    let data = self.bump.alloc_slice_copy(&data);
+                    Term::Bytes { data }
+                }
+
                 r => unreachable!("term: {:?}", r),
             };
 
diff --git a/hugr-model/src/v0/text/print.rs b/hugr-model/src/v0/text/print.rs
index 430f07e99..53bcc37b7 100644
--- a/hugr-model/src/v0/text/print.rs
+++ b/hugr-model/src/v0/text/print.rs
@@ -1,3 +1,4 @@
+use base64::{prelude::BASE64_STANDARD, Engine};
 use pretty::{Arena, DocAllocator, RefDoc};
 use std::borrow::Cow;
 
@@ -598,6 +599,15 @@ impl<'p, 'a: 'p> PrintContext<'p, 'a> {
                 this.print_text(tag.to_string());
                 this.print_term(*values)
             }),
+            Term::BytesType => {
+                self.print_text("bytes");
+                Ok(())
+            }
+            Term::Bytes { data } => self.print_parens(|this| {
+                this.print_text("bytes");
+                this.print_byte_string(data);
+                Ok(())
+            }),
         }
     }
 
@@ -717,4 +727,14 @@ impl<'p, 'a: 'p> PrintContext<'p, 'a> {
         output.push('"');
         self.print_text(output);
     }
+
+    /// Print a bytes literal.
+    fn print_byte_string(&mut self, bytes: &[u8]) {
+        // every 3 bytes are encoded into 4 characters
+        let mut output = String::with_capacity(2 + bytes.len().div_ceil(3) * 4);
+        output.push('"');
+        BASE64_STANDARD.encode_string(bytes, &mut output);
+        output.push('"');
+        self.print_text(output);
+    }
 }
diff --git a/hugr-model/tests/binary.rs b/hugr-model/tests/binary.rs
index 6a00a6b35..6120abb60 100644
--- a/hugr-model/tests/binary.rs
+++ b/hugr-model/tests/binary.rs
@@ -68,3 +68,8 @@ pub fn test_lists() {
 pub fn test_const() {
     binary_roundtrip(include_str!("fixtures/model-const.edn"));
 }
+
+#[test]
+pub fn test_literals() {
+    binary_roundtrip(include_str!("fixtures/model-literals.edn"));
+}
diff --git a/hugr-model/tests/fixtures/model-literals.edn b/hugr-model/tests/fixtures/model-literals.edn
index 552155dda..68087e37f 100644
--- a/hugr-model/tests/fixtures/model-literals.edn
+++ b/hugr-model/tests/fixtures/model-literals.edn
@@ -1,3 +1,4 @@
 (hugr 0)
 
 (define-alias mod.string str "\"\n\r\t\\\u{1F44D}")
+(define-alias mod.bytes bytes (bytes "SGVsbG8gd29ybGQg8J+Yig=="))
diff --git a/hugr-model/tests/snapshots/text__literals.snap b/hugr-model/tests/snapshots/text__literals.snap
index 4a639d8e7..e767e310a 100644
--- a/hugr-model/tests/snapshots/text__literals.snap
+++ b/hugr-model/tests/snapshots/text__literals.snap
@@ -5,3 +5,5 @@ expression: "roundtrip(include_str!(\"fixtures/model-literals.edn\"))"
 (hugr 0)
 
 (define-alias mod.string str "\"\n\r\t\\👍")
+
+(define-alias mod.bytes bytes (bytes "SGVsbG8gd29ybGQg8J+Yig=="))