diff --git a/AdventOfCode.lpi b/AdventOfCode.lpi
index 102137f..dea1b1c 100644
--- a/AdventOfCode.lpi
+++ b/AdventOfCode.lpi
@@ -49,6 +49,10 @@
         <Filename Value="solvers\UScratchcards.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="UGiveSeedFertilizer.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
     </Units>
   </ProjectOptions>
   <CompilerOptions>
diff --git a/AdventOfCode.lpr b/AdventOfCode.lpr
index 43c82a3..51224b5 100644
--- a/AdventOfCode.lpr
+++ b/AdventOfCode.lpr
@@ -25,7 +25,7 @@ uses
   {$ENDIF}
   Classes, SysUtils, CustApp,
   USolver,
-  UTrebuchet, UCubeConundrum, UGearRatios, UScratchcards;
+  UTrebuchet, UCubeConundrum, UGearRatios, UScratchcards, UGiveSeedFertilizer;
 
 type
 
@@ -54,6 +54,7 @@ begin
   engine := TSolverEngine.Create('data');
   engine.RunAndFree(TGearRatios.Create);
   engine.RunAndFree(TScratchcards.Create);
+  engine.RunAndFree(TGiveSeedFertilizer.Create);
   engine.Free;
 end;
 
diff --git a/UGiveSeedFertilizer.pas b/UGiveSeedFertilizer.pas
new file mode 100644
index 0000000..dc44a6b
--- /dev/null
+++ b/UGiveSeedFertilizer.pas
@@ -0,0 +1,208 @@
+{
+  Solutions to the Advent Of Code.
+  Copyright (C) 2023  Stefan Müller
+
+  This program is free software: you can redistribute it and/or modify it under
+  the terms of the GNU General Public License as published by the Free Software
+  Foundation, either version 3 of the License, or (at your option) any later
+  version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program.  If not, see <http://www.gnu.org/licenses/>.
+}
+
+unit UGiveSeedFertilizer;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, fgl, USolver;
+
+type
+
+  { TAlmanacMapRange }
+
+  TAlmanacMapRange = class
+  private
+    FDestinationStart, FSourceStart, FSourceEnd, FDifference1, FDifference2: Cardinal;
+  public
+    constructor Create(const ADestinationStart, ASourceStart, ALength: Cardinal);
+    function TryConvert(const AInput: Cardinal; out OOutput: Cardinal): Boolean;
+  end;
+
+  { TAlmanacMap }
+
+  TAlmanacMap = class
+  private
+    FRanges: specialize TFPGObjectList<TAlmanacMapRange>;
+  public
+    constructor Create;
+    destructor Destroy; override;
+    procedure AddMapRange(const ALine: string);
+    function Convert(const AInput: Cardinal): Cardinal;
+  end;
+
+  { TGiveSeedFertilizer }
+
+  TGiveSeedFertilizer = class(TSolver)
+  private
+    FSeeds: specialize TFPGList<Cardinal>;
+    FMaps: specialize TFPGObjectList<TAlmanacMap>;
+    procedure ProcessSeeds(const ALine: string);
+  public
+    constructor Create;
+    destructor Destroy; override;
+    procedure ProcessDataLine(const ALine: string); override;
+    procedure Finish; override;
+    function GetDataFileName: string; override;
+    function GetPuzzleName: string; override;
+  end;
+
+implementation
+
+{ TAlmanacMapRange }
+
+constructor TAlmanacMapRange.Create(const ADestinationStart, ASourceStart, ALength: Cardinal);
+begin
+  FDestinationStart := ADestinationStart;
+  FSourceStart := ASourceStart;
+
+  // All input values are within Cardinal range, but the calculations might not be.
+  if ASourceStart <= Cardinal.MaxValue - ALength then
+    FSourceEnd := ASourceStart + ALength
+  else
+    FSourceEnd := Cardinal.MaxValue;
+
+  if ADestinationStart >= ASourceStart then
+  begin
+    FDifference1 := ADestinationStart - ASourceStart;
+    FDifference2 := 0;
+  end
+  else begin
+    FDifference1 := 0;
+    FDifference2 := ASourceStart - ADestinationStart;
+  end;
+end;
+
+function TAlmanacMapRange.TryConvert(const AInput: Cardinal; out OOutput: Cardinal): Boolean;
+begin
+  if (FSourceStart <= AInput) and (AInput < FSourceEnd) then
+  begin
+    if FDifference1 > 0 then
+      OOutput := AInput + FDifference1
+    else
+      OOutput := AInput - FDifference2;
+    Result := True;
+  end
+  else begin
+    OOutput := 0;
+    Result := False;
+  end;
+end;
+
+{ TAlmanacMap }
+
+constructor TAlmanacMap.Create;
+begin
+  FRanges := specialize TFPGObjectList<TAlmanacMapRange>.Create;
+end;
+
+destructor TAlmanacMap.Destroy;
+begin
+  FRanges.Free;
+  inherited Destroy;
+end;
+
+procedure TAlmanacMap.AddMapRange(const ALine: string);
+var
+  split: TStringArray;
+begin
+  split := ALine.Split(' ');
+  FRanges.Add(TAlmanacMapRange.Create(StrToDWord(split[0]), StrToDWord(split[1]), StrToDWord(split[2])));
+end;
+
+function TAlmanacMap.Convert(const AInput: Cardinal): Cardinal;
+var
+  range: TAlmanacMapRange;
+begin
+  for range in FRanges do
+  begin
+    if range.TryConvert(AInput, Result) then
+      Exit;
+  end;
+
+  Result := AInput;
+end;
+
+{ TGiveSeedFertilizer }
+
+procedure TGiveSeedFertilizer.ProcessSeeds(const ALine: string);
+var
+  split: TStringArray;
+  i: Integer;
+begin
+  split := Aline.Split(' ');
+  for i := 1 to Length(split) - 1 do
+  begin
+    FSeeds.Add(StrToDWord(split[i]));
+  end;
+end;
+
+constructor TGiveSeedFertilizer.Create;
+begin
+  FSeeds := specialize TFPGList<Cardinal>.Create;
+  FMaps := specialize TFPGObjectList<TAlmanacMap>.Create;
+end;
+
+destructor TGiveSeedFertilizer.Destroy;
+begin
+  FSeeds.Free;
+  FMaps.Free;
+  inherited Destroy;
+end;
+
+procedure TGiveSeedFertilizer.ProcessDataLine(const ALine: string);
+begin
+  if LeftStr(ALine, 6) = 'seeds:' then
+    ProcessSeeds(ALine)
+  else if RightStr(ALine, 4) = 'map:' then
+    FMaps.Add(TAlmanacMap.Create)
+  else if Aline <> '' then
+    FMaps.Last.AddMapRange(ALine);
+end;
+
+procedure TGiveSeedFertilizer.Finish;
+var
+  seed, value: Cardinal;
+  map: TAlmanacMap;
+begin
+  for seed in FSeeds do
+  begin
+    value := seed;
+    for map in FMaps do
+    begin
+      value := map.Convert(value);
+    end;
+    if (FPart1 = 0) or (value < FPart1) then
+      FPart1 := value;
+  end;
+end;
+
+function TGiveSeedFertilizer.GetDataFileName: string;
+begin
+  Result := 'give_seed_fertilizer.txt';
+end;
+
+function TGiveSeedFertilizer.GetPuzzleName: string;
+begin
+  Result := 'Day 5: If You Give A Seed A Fertilizer';
+end;
+
+end.
+
diff --git a/tests/AdventOfCodeFPCUnit.lpi b/tests/AdventOfCodeFPCUnit.lpi
index 4f20461..6a82f6b 100644
--- a/tests/AdventOfCodeFPCUnit.lpi
+++ b/tests/AdventOfCodeFPCUnit.lpi
@@ -52,6 +52,10 @@
         <Filename Value="UScratchcardsTestCases.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="UGiveSeedFertilizerTestCases.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
     </Units>
   </ProjectOptions>
   <CompilerOptions>
diff --git a/tests/AdventOfCodeFPCUnit.lpr b/tests/AdventOfCodeFPCUnit.lpr
index 3aa8ff7..65174d4 100644
--- a/tests/AdventOfCodeFPCUnit.lpr
+++ b/tests/AdventOfCodeFPCUnit.lpr
@@ -3,7 +3,8 @@ program AdventOfCodeFPCUnit;
 {$mode objfpc}{$H+}
 
 uses
-  Interfaces, Forms, GuiTestRunner, USolver, UBaseTestCases, UGearRatiosTestCases, UScratchcardsTestCases;
+  Interfaces, Forms, GuiTestRunner, USolver, UBaseTestCases, UGearRatiosTestCases, UScratchcardsTestCases, 
+UGiveSeedFertilizerTestCases;
 
 {$R *.res}
 
diff --git a/tests/UGiveSeedFertilizerTestCases.pas b/tests/UGiveSeedFertilizerTestCases.pas
new file mode 100644
index 0000000..4e42cce
--- /dev/null
+++ b/tests/UGiveSeedFertilizerTestCases.pas
@@ -0,0 +1,89 @@
+{
+  Solutions to the Advent Of Code.
+  Copyright (C) 2023  Stefan Müller
+
+  This program is free software: you can redistribute it and/or modify it under
+  the terms of the GNU General Public License as published by the Free Software
+  Foundation, either version 3 of the License, or (at your option) any later
+  version.
+
+  This program is distributed in the hope that it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program.  If not, see <http://www.gnu.org/licenses/>.
+}
+
+unit UGiveSeedFertilizerTestCases;
+
+{$mode ObjFPC}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, fpcunit, testregistry, USolver, UBaseTestCases, UGiveSeedFertilizer;
+
+type
+
+  { TGiveSeedFertilizerFullDataTestCase }
+
+  TGiveSeedFertilizerFullDataTestCase = class(TEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart1;
+    procedure TestPart2;
+  end;
+
+  { TGiveSeedFertilizerExampleTestCase }
+
+  TGiveSeedFertilizerExampleTestCase = class(TExampleEngineBaseTest)
+  protected
+    function CreateSolver: ISolver; override;
+  published
+    procedure TestPart1;
+    procedure TestPart2;
+  end;
+
+implementation
+
+{ TGiveSeedFertilizerFullDataTestCase }
+
+function TGiveSeedFertilizerFullDataTestCase.CreateSolver: ISolver;
+begin
+  Result := TGiveSeedFertilizer.Create;
+end;
+
+procedure TGiveSeedFertilizerFullDataTestCase.TestPart1;
+begin
+  AssertEquals(51580674, FSolver.GetResultPart1);
+end;
+
+procedure TGiveSeedFertilizerFullDataTestCase.TestPart2;
+begin
+  AssertEquals(-1, FSolver.GetResultPart2);
+end;
+
+{ TGiveSeedFertilizerExampleTestCase }
+
+function TGiveSeedFertilizerExampleTestCase.CreateSolver: ISolver;
+begin
+  Result := TGiveSeedFertilizer.Create;
+end;
+
+procedure TGiveSeedFertilizerExampleTestCase.TestPart1;
+begin
+  AssertEquals(35, FSolver.GetResultPart1);
+end;
+
+procedure TGiveSeedFertilizerExampleTestCase.TestPart2;
+begin
+  AssertEquals(-1, FSolver.GetResultPart2);
+end;
+
+initialization
+
+  RegisterTest(TGiveSeedFertilizerFullDataTestCase);
+  RegisterTest(TGiveSeedFertilizerExampleTestCase);
+end.