diff --git a/src/lib.rs b/src/lib.rs
index aaa7dfb..a6255d3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,7 @@ pub mod encoding;
 pub mod seed;
 pub mod signing;
 pub mod spendpolicy;
+pub mod transactionbuilder;
 pub mod transactions;
 pub mod unlock_conditions;
 
diff --git a/src/transactionbuilder.rs b/src/transactionbuilder.rs
new file mode 100644
index 0000000..1da7a3e
--- /dev/null
+++ b/src/transactionbuilder.rs
@@ -0,0 +1,147 @@
+use crate::{
+    encoding::SerializeError,
+    signing::SigningState,
+    transactions::{CoveredFields, SiacoinOutput},
+    Address, Currency, Hash256,
+};
+use thiserror::Error;
+
+use crate::{
+    signing::PrivateKey,
+    transactions::{SiacoinInput, SiacoinOutputID, Transaction},
+    unlock_conditions::{UnlockConditions, UnlockKey},
+};
+
+#[derive(Error, Debug)]
+pub enum Error {
+    #[error("Transaction serialization error: {0}")]
+    Serialize(#[from] SerializeError),
+}
+
+#[derive(Debug, PartialEq)]
+pub struct TransactionBuilder {
+    transaction: Transaction,
+}
+
+// NOTE: instead of using the builder pattern, we could also return a ToSign
+// when we add inputs and leave it to the caller to track the ToSign instances
+// they want to use for signing later.
+pub struct ToSign {
+    parent_id: Hash256,
+    public_key_index: u64,
+}
+
+/// TODO: Missing features
+/// - Add change output
+/// - Add FileContract
+/// - Add FileContractdRevision
+/// - Add StorageProof
+/// - Add SiafundInput
+/// - Add SiafundOutput
+/// - Add MinerFee
+/// - Add ArbitraryData
+/// - Add Signature
+
+impl TransactionBuilder {
+    /// Creates a new transaction builder
+    pub fn new() -> TransactionBuilder {
+        TransactionBuilder {
+            transaction: Default::default(),
+        }
+    }
+
+    pub fn add_change_address(self, _address: Address) -> Self {
+        unimplemented!(
+            "if inputs exceed outputs, add an output that send the change to the provided address"
+        )
+    }
+
+    pub fn add_miner_fee(mut self, fee: Currency) -> Self {
+        self.transaction.miner_fees.push(fee);
+        self
+    }
+
+    /// Adds a siacoin input with a simple 'spendable by public key' unlock
+    /// condition
+    pub fn add_siacoin_input(mut self, parent_id: SiacoinOutputID, public_key: UnlockKey) -> Self {
+        self.transaction.siacoin_inputs.push(SiacoinInput {
+            parent_id: parent_id,
+            unlock_conditions: UnlockConditions {
+                public_keys: vec![public_key],
+                timelock: 0,
+                signatures_required: 1,
+            },
+        });
+        self
+    }
+
+    /// Adds a siacoin output with the given value to the transaction
+    pub fn add_siacoin_output(mut self, address: Address, value: Currency) -> Self {
+        self.transaction.siacoin_outputs.push(SiacoinOutput {
+            address: address,
+            value: value,
+        });
+        self
+    }
+
+    /// Finalizes the transaction, consuming the builder.
+    pub fn finalize(self) -> Transaction {
+        self.transaction
+    }
+
+    /// Signs the whole transaction with the provided private key for each input
+    /// in to_sign. The public_key_index is the index of the public key within
+    /// the unlock conditions of the input that we sign for.
+    pub fn sign(
+        mut self,
+        state: &SigningState,
+        to_sign: &[ToSign],
+        timelock: u64,
+        private_key: &PrivateKey,
+    ) -> Result<Self, Error> {
+        // cover everything
+        let mut covered_fields = CoveredFields::default();
+        for i in 0..self.transaction.siacoin_inputs.len() {
+            covered_fields.siacoin_inputs.push(i);
+        }
+        for i in 0..self.transaction.siacoin_outputs.len() {
+            covered_fields.siacoin_outputs.push(i);
+        }
+        for i in 0..self.transaction.file_contracts.len() {
+            covered_fields.file_contracts.push(i);
+        }
+        for i in 0..self.transaction.file_contract_revisions.len() {
+            covered_fields.file_contract_revisions.push(i);
+        }
+        for i in 0..self.transaction.storage_proofs.len() {
+            covered_fields.storage_proofs.push(i);
+        }
+        for i in 0..self.transaction.siafund_inputs.len() {
+            covered_fields.siafund_inputs.push(i);
+        }
+        for i in 0..self.transaction.siafund_outputs.len() {
+            covered_fields.siafund_outputs.push(i);
+        }
+        for i in 0..self.transaction.miner_fees.len() {
+            covered_fields.miner_fees.push(i);
+        }
+        for i in 0..self.transaction.arbitrary_data.len() {
+            covered_fields.arbitrary_data.push(i);
+        }
+        for i in 0..self.transaction.signatures.len() {
+            covered_fields.signatures.push(i);
+        }
+        for ts in to_sign {
+            let signature = self.transaction.sign(
+                state,
+                &covered_fields,
+                ts.parent_id,
+                ts.public_key_index,
+                timelock,
+                private_key,
+            )?;
+            self.transaction.signatures.push(signature);
+        }
+        Ok(self)
+    }
+}
diff --git a/tests/transactionbuilder.rs b/tests/transactionbuilder.rs
new file mode 100644
index 0000000..7e6e36c
--- /dev/null
+++ b/tests/transactionbuilder.rs
@@ -0,0 +1,10 @@
+extern crate sia_core;
+
+use sia_core::transactionbuilder::*;
+use sia_core::transactions::Transaction;
+
+#[test]
+fn test_transactionbuilder_new() {
+    let transaction = TransactionBuilder::new().finalize();
+    assert_eq!(transaction, Transaction::default());
+}