diff --git a/crates/domain/src/error.rs b/crates/domain/src/error.rs
index ed97982..6272965 100644
--- a/crates/domain/src/error.rs
+++ b/crates/domain/src/error.rs
@@ -8,4 +8,5 @@ pub enum KernelError {
     NoFreeSlot,
     InvalidProcess(ProcessId),
     WouldBlock,
+    TooManyThreadsInProcess,
 }
diff --git a/crates/domain/src/process/mod.rs b/crates/domain/src/process/mod.rs
new file mode 100644
index 0000000..cf9c0f2
--- /dev/null
+++ b/crates/domain/src/process/mod.rs
@@ -0,0 +1,73 @@
+use types::{
+    bounded::CapSlot,
+    id::{ProcessId, ThreadId},
+};
+
+use crate::capability::CapabilityTable;
+
+#[cfg(test)]
+#[path = "tests.rs"]
+mod tests;
+
+pub const MAX_THREADS_PER_PROCESS: usize = 4;
+
+pub struct Process {
+    id: ProcessId,
+    capabilities: CapabilityTable,
+    threads: [Option<ThreadId>; MAX_THREADS_PER_PROCESS],
+    fault_handler: Option<CapSlot>,
+}
+
+impl Process {
+    pub fn new(
+        id: ProcessId,
+        capabilities: CapabilityTable,
+        fault_handler: Option<CapSlot>,
+    ) -> Self {
+        Self {
+            id,
+            capabilities,
+            threads: [None; MAX_THREADS_PER_PROCESS],
+            fault_handler,
+        }
+    }
+
+    pub fn id(&self) -> ProcessId {
+        self.id
+    }
+
+    pub fn capabilities(&self) -> &CapabilityTable {
+        &self.capabilities
+    }
+
+    pub fn capabilities_mut(&mut self) -> &mut CapabilityTable {
+        &mut self.capabilities
+    }
+
+    pub fn fault_handler(&self) -> Option<CapSlot> {
+        self.fault_handler
+    }
+
+    pub fn add_thread(&mut self, thread: ThreadId) -> Result<(), crate::error::KernelError> {
+        let slot = self
+            .threads
+            .iter_mut()
+            .find(|s| s.is_none())
+            .ok_or(crate::error::KernelError::TooManyThreadsInProcess)?;
+        *slot = Some(thread);
+        Ok(())
+    }
+
+    pub fn remove_thread(&mut self, thread: ThreadId) {
+        for slot in &mut self.threads {
+            if *slot == Some(thread) {
+                *slot = None;
+                return;
+            }
+        }
+    }
+
+    pub fn thread_ids(&self) -> impl Iterator<Item = ThreadId> + '_ {
+        self.threads.iter().filter_map(|s| *s)
+    }
+}
diff --git a/crates/domain/src/process/tests.rs b/crates/domain/src/process/tests.rs
new file mode 100644
index 0000000..3071dcc
--- /dev/null
+++ b/crates/domain/src/process/tests.rs
@@ -0,0 +1,78 @@
+use super::*;
+use crate::capability::CapabilityTable;
+use types::bounded::CapSlot;
+use types::id::{ProcessId, ThreadId};
+
+fn thread(id: u16) -> ThreadId {
+    ThreadId::from_raw(id)
+}
+
+fn test_process(id: u16) -> Process {
+    Process::new(ProcessId::from_raw(id), CapabilityTable::new(), None)
+}
+
+#[test]
+fn new_process_has_no_threads() {
+    let p = test_process(0);
+    assert_eq!(p.thread_ids().count(), 0);
+}
+
+#[test]
+fn id_matches_construction() {
+    let p = test_process(42);
+    assert_eq!(p.id(), ProcessId::from_raw(42));
+}
+
+#[test]
+fn fault_handler_none_by_default() {
+    let p = test_process(0);
+    assert!(p.fault_handler().is_none());
+}
+
+#[test]
+fn fault_handler_preserved() {
+    let slot = CapSlot::new(5).unwrap();
+    let p = Process::new(ProcessId::from_raw(0), CapabilityTable::new(), Some(slot));
+    assert_eq!(p.fault_handler(), Some(slot));
+}
+
+#[test]
+fn add_and_iterate_threads() {
+    let mut p = test_process(0);
+    p.add_thread(thread(0)).unwrap();
+    p.add_thread(thread(1)).unwrap();
+    assert_eq!(p.thread_ids().count(), 2);
+    assert!(p.thread_ids().any(|t| t == thread(0)));
+    assert!(p.thread_ids().any(|t| t == thread(1)));
+}
+
+#[test]
+fn add_thread_beyond_max_fails() {
+    let mut p = test_process(0);
+    for i in 0..MAX_THREADS_PER_PROCESS {
+        p.add_thread(thread(i as u16)).unwrap();
+    }
+    assert!(p.add_thread(thread(99)).is_err());
+}
+
+#[test]
+fn remove_thread_frees_slot() {
+    let mut p = test_process(0);
+    p.add_thread(thread(0)).unwrap();
+    p.remove_thread(thread(0));
+    assert_eq!(p.thread_ids().count(), 0);
+    p.add_thread(thread(1)).unwrap();
+    assert_eq!(p.thread_ids().count(), 1);
+}
+
+#[test]
+fn capabilities_accessible() {
+    let p = test_process(0);
+    let _caps = p.capabilities();
+}
+
+#[test]
+fn capabilities_mut_accessible() {
+    let mut p = test_process(0);
+    let _caps = p.capabilities_mut();
+}